Authoring Questions in ACE

Any ACE instructor can author his or her own questions or modify database questions. If you modify a database question, the changes will propagate into all of your courses, but not any other instructor's courses, so they will be visible to you and your students but no others. Likewise, if you author a question from scratch, the question will be visible only to you and students in your courses. (Exception: If another instructor designates you as a coinstructor of a course, you may assign the work you do in an authoring session to that instructor. In this case, the work that you do will be visible only to students in the courses created by your coinstructor.) However, you may share your questions with other instructors if you wish to do so.

Most instructors modify database questions simply to reword the question statement or feedback more to their taste. Occasionally, however, an instructor will find an error — a correct question marked as incorrect, or vice versa, or feedback completely irrelevant to a particular response. If you find an error, by all means, feel free to correct it yourself, but please contact Bob Grossman to alert him to the error so he can correct it in the database.

Some instructors are more ambitious, wanting to author their own questions in ACE. Authoring questions in ACE is an art. As such, learning how to do it requires practice and patience. We strongly suggest that beginners find questions in ACE to use as models for new questions.

A question consists of the following parts:


The question statement

The question statement is exactly what its name says it is. ACE will save a question only if it has either a statement or a figure. ACE formats the question statement automatically.

The question statements of fill-in-the-blank questions require a special format.

If the question set in which a question resides has a common question statement, then, when ACE displays any question in that set to a student, it appends the common question statement to the beginning of the question's own statement. If you are writing a series of questions that all use the same statement, consider putting the entire series in its own question set and writing a common question statement for the entire set. That way, you don't need to write it out for every question, and, if you decide to change it, the change will be effective in every question simultaneously.


Evaluators

An evaluator determines whether a student's response has a particular property. The English description of evaluators usually begins, "If the response...." ACE has almost fifty different kinds of evaluators at this time, although ACE makes only a subset available for each question type.

A question may have any number of evaluators. The list of evaluators acts as a hierarchical sieve; that is, ACE tests the response against each evaluator in order, and the first evaluator that the response satisfies determines the student's grade (between 0 and 1, set by the author except when the complete-the-table evaluator TableDiff, the mechanism evaluator MechCounter, or the multistep synthesis evaluator SynthSteps calculates it from the response) and feedback.

The feedback is what turns students' errors into learning opportunities, so it is important to think carefully about how to write it. It is usually best to tell the student what is wrong with the response he or she provided, not to tell the student what the desired answer is or how to correct an incorrect response. Furthermore, it is important to provide feedback even for correct responses. Students sometimes arrive at the answer without quite knowing how they did so, and good feedback for correct responses may help solidify their their skills. Just as it does question statements, ACE formats feedback automatically.

Some evaluators generate feedback automatically, appending the author-written feedback (if any) to the automatically generated feedback. The feedback automatically generated by MechFlowsValid, SynthScheme, and SynthSelective evaluators is usually sufficiently descriptive that the author does not need to provide any additional feedback.

Authors may combine evaluators logically to make a complex evaluator. For example:

3 [W] 3.1 and (3.2 or 3.3)
3.1 If the number of C atoms is equal to 6
3.2 If the number of O atoms is equal to 1
3.3 If the number of N atoms is equal to 1

Authors choose a grade and write feedback only for the top level of a complex evaluator (in the example, line 3). Authors may modify the subevaluators (lines 3.1, 3.2, and 3.3) or change the logic of combining them. If a subevaluator generates automatic feedback, then the combined evaluator will return that automatic feedback if the subevaluator is the last individual expression of an OR expression or the first individual expression of an AND expression.

Because the list of evaluators acts as a hierarchical sieve, the order in which an author lists evaluators can be very important. ACE does not use evaluators subsequent to the satisfied one to evaluate the response. Consequently, if evaluator 1 is, "If the total charge on the response is not 0," then an author can assume that subsequent evaluators will encounter no response with a positive or negative total charge.


Formatting text in ACE

Because we designed ACE for organic chemistry, ACE recognizes common organic chemistry expressions in unformatted or lightly formatted text and formats them appropriately. For example, when an author types "C5H5^- does SN2", ACE displays "C5H5 does SN2" to users.

ACE applies its formatting rules to question statements, feedback, ordering/ranking and multiple-choice options, fill-in-the-blank pulldown menus, structure names, and the titles of assignments. Authors who wish to learn more about ACE's formatting rules should consult this public-access page. It has an interactive feature that allows authors to type various expressions and see how ACE will format them.

ACE does not apply formatting to draw-vectors or equations questions, as these questions are used for subjects other than organic chemistry.

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Testing for configurational stereochemistry

Many evaluators in ACE compare the structure or structures in a student's response to one or more structures provided by the author. Authors can easily test, or choose not to test, whether the structures in the response have a particular stereochemical configuration.

MarvinJS has four single-bond types to indicate tetrahedral stereochemistry: bold, hashed, wavy, and straight. The first two specify configuration as R or S, the third specifies a mixture of R and S, and the last leaves the configuration unspecified. (Note: In three-dimensional structures, Marvin uses the structure's 3D coordinates to determine configurations. It ignores bold, hashed, and wavy bonds.)

Authors specify double bond stereochemistry by the physical coordinates of the substituents of the double bond. Marvin provides three ways for an author to indicate unspecified double-bond configuration:

The stereochemistry matching rules are:

All evaluators that compare author structures to student structures (except the skeletons mode of Contains) use these matching rules. The most frequently used evaluators for this purpose are Is and Contains, but the rules also apply to MapProperty, MechProdStartIs, and a few others.

If a student's response should have a particular configuration at a stereocenter, it is useful to test both for particular configurations as well as for no configuration at all. For example, if the student is supposed to draw (S)-2-butanol, it is useful to write a correct-response evaluator for (S)-2-butanol and incorrect-response evaluators for (R)-2-butanol, (RS)-2-butanol (wavy bond), and 2-butanol with no configuration specified. Each incorrect-response evaluator should have different feedback, because the intellectual error that the student has made in each case is different. It is important to remember that the order of the evaluators matters. If the unspecified 2-butanol evaluator comes first, then no response will satisfy the (R)- and (RS)-2-butanol evaluators, because any response that would have satisfied one of those evaluators would have already satisfied the unspecified 2-butanol evaluator. The unspecified-configuration evaluator should always follow the specified-configuration evaluators.

Authors should also note the flag in the Is evaluator that allows them to determine how many times a particular structure or its enantiomer appears in a response. This flag is especially useful in draw-the-product questions when the reaction is diastereoselective but not enantioselective.

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Substructures and skeletons

One of the evaluators available for many question types is Contains, which determines how many compounds in the response contain a substructure or skeleton drawn by the author.

Compound A contains a substructure S if each of the following conditions is satisfied.

Compound A contains a skeleton S if each of the following conditions is satisfied.

If you wish to see whether a particular substructure is contained in a response, and you wish to exclude substitution at a particular atom in the substructure, draw explicitly all the H atoms attached to that atom.

One very useful feature of the Contains substructure search is that you may search for special atom and bond types such as "any" atoms, aromatic or nonaromatic C, single-or-double bonds, etc. See the JChem query guide for more information.

We have created an interactive Web page where you can draw a substructure or skeleton, enter various responses, and see which responses contain the substructures or skeletons.

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Lewis structure questions

In a Lewis structure question, a student responds not with ACE's standard structure-drawing program, MarvinJS, but with a stripped-down version that we wrote ourselves, which we call LewisJS. LewisJS does not highlight valence errors or show automatically the appropriate number of H atoms on heteroatoms, and, although it is now possible to indicate stereochemistry in LewisJS, ACE always ignores it. However, LewisJS has one key feature that both versions of Marvin lack, and that is the ability to add any number of unshared electrons to each atom in the structure.

ACE provides the following evaluators for Lewis structure questions.

We have found the following order of evaluators useful when writing Lewis structure questions.

  1. Use LewisIsomorph to see if the response is correct.
  2. Use LewisIsomorph to see if the student merely forgot to add in the unshared electrons.
  3. Use HasFormula to see if the formula is incorrect.
  4. Use Is to see if the σ-bond network of the response is incorrect.
  5. Use LewisValenceTotal to see if the student has placed the incorrect total number of electrons (bonds + unshared electrons) on the structure.
  6. Use LewisOuterNumber to see if the student has violated the octet rule.
  7. Use LewisFormalCharge to see if any atoms have an incorrect formal charge.

    At this point, if the student's response has still not satisfied any evaluators, it is a proper resonance structure of the correct answer.

  8. Use LewisIsomorph or LewisElecDeficientNumber to see how the student's resonance form differs from the correct answer, and craft feedback accordingly. For example, you may wish the student to draw the best resonance structure of an iminium ion, and the student may have drawn the C(+) form.
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Skeletal structure questions

The original, and still by far the most abundant, ACE question type is the skeletal structure question. Students use MarvinJS to draw one structure or a small number of structures. Skeletal structure questions can cover topics such as:

ACE provides the following evaluators for skeletal structure questions.

For most skeletal structure questions, we find that it is most useful to make the first two incorrect-response evaluators,

  1. If the number of molecules in the response is not equal to 1 ...
  2. If the total charge is not equal to 0 ...

Beyond that, authors should think about the characteristics that a correct response would have and write evaluators that test for the absence of each of these properties in turn.

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R-group questions

The R-group question is a special kind of skeletal structure, mechanism, or synthesis question that allows instructors to deliver a different version of the same question to each student.

An R-group question has the following features:

When an author selects the "uses R groups" checkbox, ACE makes visible the question data table. The author should add as many question data as there are numbered generic R groups in Figure 1. For each numbered generic R group, the author should select one or more R-group classes, such as "small alkyl groups" or "acyl groups". When a student first views a question, ACE replaces each numbered generic R group in the student's Figure 1 with one of the groups in the R-group classes that the author has selected for that particular Rn. We call the groups now in Figure 1 instantiated R groups. The instantiated R groups subsequently remain fixed for that student and that question.

Authors should write evaluators for R-group questions as if the student's response will contain the original generic R group. ACE will automatically account for the instantiated R groups that the student's response ought to contain when it evaluates it. For example, if the question is, "Draw the product of the following reaction," and Figure 1 contains "R1CH2Br + NaOCH2R2 → ", then the evaluator for the correct response would be, "If the only compound in the response is R1CH2OCH2R2...", and an evaluator for the incorrect formula would read, "If the response does not have the formula C2H4O..." (the formula omits the Rn groups). The only evaluator that does not account for the instantiated R groups that ought to be present in a student's response is the Contains evaluator. Authors of R-group questions should search for substructures and skeletons only when the search will give the same result regardless of which instantiated R group ACE may have chosen in a particular case.

ACE can also generate numeric questions algorithmically.

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Conformation questions

ACE allows authors to ask questions about chair conformations and conformations about a C(sp3)–C(sp3) bond.

ACE provides two ways for students to draw 3D chair conformations and one way to draw them as 2D projections.

In the case of single-bond conformations, students may use one of the perspective or Newman projection templates provided by Marvin. The C atoms in the ethane template are marked so that ACE knows to analyze the conformation about their bond.

Currently, ACE is able to analyze the conformations of C(sp3)–C(sp3) bonds only.

Before determining whether the student has drawn the correct conformer, you need to check first that he or she has drawn the correct configurational stereoisomer. If the student will be drawing a 2D projection of a chair, use Is2DChair to ascertain that the student has drawn the correct configurational stereoisomer; otherwise, use Is.

Important: Once a structure is in 3D, ACE ignores bold and hashed bonds. To make these bonds have effect, the user must convert back to 2D stereochemistry by typing control-2.

ACE provides one evaluator, ConformChair, for analyzing chair conformations, and one, ConformBond, for analyzing single-bond conformations, as well as most of the evaluators for skeletal structure questions. In both conformation evaluators, the author must provide the name of the group or groups whose orientation ACE must analyze. The group name must be either:

(You can find the SMILES definition of a group by drawing it in MarvinJS attached to Li, pressing the Export button (third button in northern toolbar; its icon is an old floppy disk), and from the Format pulldown menu, choosing SMILES. Delete the leading [Li] to get the group's SMILES definition. Note that SMILES definitions usually omit H atoms. ACE assumes that the first atom of the SMILES definition is attached to the C of the cyclohexane ring or rotatable bond. This assumption will be valid when you use the just-described method to craft your SMILES definition.)

ConformChair analyzes the number of times a group is axial or equatorial on a particular ring, and ConformBond determines the relative orientation (eclipsed, gauche, etc.) of two groups, one on each atom of the C–C bond that derives from the original ethane template. To choose the ring whose conformation it will analyze, ConformChair first looks for a six-membered ring in which all of the ring atoms are invisibly marked (i.e., that the student copied from the Templates menu.) In the absence of that, it looks for any saturated cyclohexane ring. (Exocyclic double bonds are permitted.) In the absence of that, it looks for a saturated six-membered ring with one heteroatom, and, in the absence of that, it looks for a saturated six-membered ring with any number of heteroatoms.

Your correct-response evaluator for a conformation question should be complex: for example, "If the response is X or its enantiomer AND if the response has one axial Br group...." If this evaluator is not satisfied, then write incorrect-response evaluators that test for various ways that the structure of the response may differ from X or its enantiomer. For example, you may use Is to test if the student has drawn an incorrect diastereomer, or if the student's response has the wrong formula. Your last evaluator in this section should be, "If the response is not X or its enantiomer...." If the response does not satisfy this evaluator, then the response must have the right structure, but be in the wrong conformation. You can use the conformation evaluators to determine how the conformation might be incorrect and provide appropriate feedback.

ACE may generate automatic feedback if it finds a group that it cannot assign as axial or equatorial.

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Atom mapping or selection questions

In an atom mapping or selection question, a student either selects one or more atoms in a structure, or marks one or more atoms in a structure with numbers between 1 and 99. ACE treats the selection of atoms as equivalent to marking them with the number 1.

Most mapping questions requires students to use particular numbers. For example, a question might ask a student to mark atoms with 1, 2, or 3, depending on whether the atom is sp-, sp2-, or sp3-hybridized. This kind of question is called an "exact map". However, there are some mapping questions that require that atoms that share a particular property have the same number, but it does not matter what number it is. For example, a student might be asked to label H atoms that are isochronous in the 1H NMR spectrum with identical numbers, and anisochronous H atoms with different numbers. This kind of question is called a "map pattern". If a question asks students to select atoms, all selected atoms will be marked with the number 1, so there will be no difference between the map pattern and the exact map.

ACE provides two evaluators, MapProperty and MapSelectionsCounter, for analyzing mapping, as well as most of the evaluators for skeletal structure questions. The evaluator MapSelectionsCounter always calculates a student's grade based on the extent to which ae student's selections match the quthor's selections, adding or subtracting an amount of credit chosen by the author for each match or mismatch.

If a structure contains shortcut groups, MapProperty and MapSelectionsCounter ungroup them. If any shortcut group has been mapped, the evaluator places its map number on the atom of the group that is attached to the rest of the structure. The evaluators consider all implicit H atoms to be unmapped.

Take care if you are using 3D mode in mapping questions with multiple structures. If mapping of one structure in the response converts a meso structure into an asymmetric one, then the combination of the newly asymmetric structure with a preexisting chiral structure can give diastereomers, which may or may not match with one another. Furthermore, JChem will assign a configuration to a stereocenter, even if you draw the structure in such a way that it appears to have an unspecified configuration, and even if you include a wavy bond.

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Mechanism and resonance structure questions

Mechanism questions are one of the two most complex types in ACE (the other being multistep synthesis), and they are certainly among the most difficult to author.

The first thing to realize about mechanism questions in ACE is that ACE does not determine whether a mechanism response is "correct". Instead, ACE determines whether a mechanism response violates any of the rules that organic chemists have developed over the years about mechanisms. If a mechanism response does not violate any rules, then ACE considers it to be correct. This approach to mechanisms is necessitated by the fact that there are often many correct ways to draw a mechanism — for example, with or without particular resonance forms — and even sometimes more than one acceptable mechanism, and we do not want authors to have to enter every possibility into ACE.

To be more specific, an ACE mechanism question has a series of incorrect-response evaluators that determine whether a response violates any rules, followed by a single correct-response evaluator, "If the number of C atoms is greater than 0...." If a response satisfies none of the incorrect-response evaluators, it will satisfy the last one, so it will be marked correct.

(An exception to this general approach is warranted if the mechanism is very short and unambiguous. For example, if you have provided a student with starting materials and products, and you want the student only to draw electron-flow arrows, you can write a correct-response evaluator that evaluates whether the appropriate compounds and electron-flow arrows are present in a stage of the mechanism.)

In general, a mechanism is correct if,

Below is an example of a correctly drawn ACE mechanism for the reaction, "acetone + EtONa + Br2 → bromoacetone". Note that the student has omitted the EtOH and Br coproducts, as per the common convention, although students may draw them if they wish, and a question author may require students to draw them. Note also that the student has chosen to draw the enolate in both resonance forms. ACE would consider the mechanism to be correct if the student drew just one or the other resonance form as long as the student still drew the electron-flow arrows appropriately.

nochain

It can be difficult to draw mechanisms of free-radical chain reactions in the proper form in ACE. Here is an example of a correctly drawn radical chain mechanism for the reaction, "3-bromoTHF + Bu3SnH + cat. (BzO)2 → THF".

chain

Note several aspects of this drawing:

An author does not need to write an evaluator to determine whether the form of a mechanism response is correct. ACE automatically evaluates the form of the response when a student submits it. If ACE is unable to parse the response, it provides appropriate feedback and may highlight the offending aspect of the response (for example, a rectangle that contains no electron-flow arrows).

The evaluators that ACE makes available to authors of mechanism questions are as follows.

We have found the following order of evaluators useful for mechanism questions.

  1. Determine whether the specified product of the mechanism is actually present in the response as a product. Use MechProdStartIs to ask, "If, given these products, not all are present in the response...." Include only products that you would require a student to draw. For example, in the mechanism for RONa + CH3I, you would probably not require a student to draw NaI or I.
  2. Determine whether the student uses as starting materials all of the compounds you expect the student to use.
  3. Use the MechRule evaluator to determine if the class of mechanism is incorrect. For example, if the mechanism should be polar, does the student use radicals? If the reaction conditions are acidic, does the student generate strong bases?
  4. Use the Is evaluator to determine if any key intermediates are absent from the mechanism.
  5. Use the MechFlowsValid evaluator to determine if the response uses electron-flow arrows correctly and if all of the compounds not produced by electron-flow arrows are permissible starting materials. In this evaluator, you should list every starting material that the student might permissibly use. For example, if one of the starting materials is HBr, you should list HBr, H+, and Br. Check the "resonance-permissive" box if the student may use any resonance structure of the starting materials.
  6. Use the MechSubstructure evaluator to determine if there are any specific mechanistic steps that the student may have incorrectly included or omitted. For example, you may want to look for a concerted carbonyl-enol tautomerization or a four-centered TS for proton transfer.
  7. Use the MechRule evaluator to determine if the student has broken any other relevant heuristic rules. For example, does the student propose an SN2 substitution at an sp2-hybridized C atom? Does the response have a multiply charged intermediate? The last few incorrect-response evaluators should check for violations of mechanism conventions such as the inappropriate use or disuse of resonance arrows. We usually give 50% credit if the only error is a convention violation.
  8. Finally, use the Atoms evaluator to determine if the response contains any C atoms. If it does, and it has not satisfied any prior evaluators, it is correct.
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Resonance structure questions

Resonance structure questions that ask the student to draw electron-flow arrows are a subset of mechanism questions. In a typical resonance structure question, the author provides two boxes connected by a resonance arrow, with a structure in one of the boxes, and the student must draw both a good resonance structure and the electron-flow arrows on the given structure that lead to the resonance structure. We have found the following sequence of evaluators useful for resonance structure questions.

  1. Use Is to ascertain that the student did not alter the given structure.
  2. Use NumMols to ascertain that there are two structures in the response.
  3. Use Charge to ascertain that the total charge of the response is twice that of the given structure.
  4. Use HasFormula to ascertain that both compounds in the response have the formula of the given structure.
  5. Use Is to determine whether every structure in the compound is identical to the given structure (i.e., whether the student simply redrew the starting structure).
  6. Use Is to determine whether every structure in the response is the given structure or a resonance structure of it. If not, the student has drawn a compound that is not a resonance structure. (You may wish to use this evaluator twice in combination with MechFlowsValid: once to see if the electron-flow arrows correctly lead to the nonresonance structure, and once to see if they do not.)
  7. Use MechFlowsValid to determine whether the student's electron-flow arrows lead to their resonance structure.
  8. Use Is to determine whether the student has not drawn the resonance structure you have asked them to draw.
  9. Use MechRule to determine whether any atom simultaneously receives and supplies unshared electrons.
  10. Use Atoms to write a correct-response evaluator, "If the number of C atoms is greater than 0...."
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Multistep synthesis questions

Multistep synthesis questions have several similarities to mechanism questions.

There are also major differences between multistep synthesis and mechanism questions, as illustrated by the response reproduced below.

synth

In general, a multistep synthesis is correct if,

The author of a multistep synthesis question defines the permissible starting materials separately from the evaluators. Permissible starting materials may be specific compounds, may have a certain number of contiguous or total C atoms, may have one or more particular functional groups, may or may not have a particular formula, may have a certain number of rings, may be uncharged and free of alkali metals and Mg, or may be free of other metals of various kinds. The author may combine these rules in any logical way. ACE considers all compounds chosen from the reaction conditions menu to be permissible starting materials. In synthesis questions that use R-groups, an author should use great caution before defining a permissible starting material as one that has no more than n contiguous C atoms, as ACE is unable to account for variability among the sizes of the students' instantiated R groups when determining whether a student's starting material is permissible.

The evaluators that ACE makes available to authors of synthesis questions are as follows.

Instructors assembling an assignment that contains one or more synthesis questions may allow students to choose from any of the reaction conditions in the database, or they may restrict the reaction conditions available to the students.

When writing multistep synthesis questions, the author may wish to use the SynthOneRxn evaluator to work around some of the selectivity prediction problems that may arise for particular reactions such as electrophilic aromatic substitutions.

If you want us to add a reaction condition to the menu, or if you find an error in the prediction of a particular reaction's products, please contact Bob Grossman.

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Orbital energy diagram questions

In the orbital energy diagram question, a student must place atomic and molecular orbitals correctly in three columns and indicate their correct occupancies and correlations. The question author determines how many rows the diagram has. The question author may also ask the student to label the molecular orbitals (in the middle column of the diagram) with labels set by the author. This last feature allows the author to ask students to associate orbitals in the diagram with pictures of orbitals.

ACE makes the following evaluators available for this type of question.

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Reaction coordinate diagram questions

In the reaction coordinate diagram question, a student must place energy maxima or minima correctly in several columns and correlate and label them correctly (for example, as "transition state" or "intermediate 1"). The question author determines how many rows and columns the diagram has.

ACE makes the following evaluators available for this type of question.

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Formula questions

In the formula question, a student enters a formula. Currently, the formula must be uncharged, and the only isotopes that ACE recognizes are D and T. ACE accepts formulas that use parentheses and those in which students do not properly capitalize the elemental symbols, the elements are not listed in Hill order, or the elements are listed more than once (e.g., CH3COOH). By contrast, unknown elemental symbols and characters other than parentheses in a response formula will cause ACE to reject the response, although ACE will not count such a response toward the total number of allowed attempts.

ACE makes the following evaluators available for this type of question.

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Multiple-choice and ordering/ranking questions

In multiple-choice and ordering questions, students are given a series of options from which they select (multiple-choice) or which they number.

The author enters the options as question data. ACE creates a place for the author to enter question data when the author chooses a question type that requires them. Each option may be text or a Marvin structure. If it is a Marvin structure, the author also enters a name for the structure. ACE uses the name for short displays of questions, as in the list of all questions in the assignment, the homework assembly tool, and the question set view in the authoring tool. Students will see the structure (and not the name) when they respond to a question or print out an entire assignment. If the option is text, ACE will format it according to its formatting rules.

In multiple-choice questions, an author decides whether to allow a student to choose multiple options. (ACE permits it by default.)

In an ordering question, an author can choose whether to allow a student to leave some items unordered.

The evaluators for multiple-choice and ordering questions are self-evident and need no explanation.

We strongly urge authors to use multiple-choice questions only when no other question type will do.

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Fill-in-the-blank questions

A fill-in-the-blank question is simply a multiple-choice question in which the author has chosen to organize the options into pulldown menus that appear in the text of the question statement. The question data that represent fill-in-the-blank options must be text. (ACE formats them according to its formatting rules.) The notation [[ ]] indicates where in the question statement ACE should insert a pulldown menu. The double brackets contain a comma-separated list of numbers, which correspond to the question data that that menu should contain. A typical fill-in-the-blank question statement and question data might be,

The most nucleophilic halide is [[1, 2, 3, 4]] because [[5, 6, 7, 8]].
  1. F^-
  2. Cl^-
  3. Br^-
  4. I^-
  5. it is most basic
  6. it is least basic
  7. it is most solvated
  8. it is least solvated

The student will see the question statement in this format:

The most nucleophilic halide is
because

ACE has no restrictions on how many options the author may include in each menu or their sequence among or within menus, although it is easier to write evaluators when one lists the options in the same sequence that they appear in the menus.

ACE makes one evaluator, MultipleCheck, available for fill-in-the-blank questions. MultipleCheck determines, "If the student has (or has not) chosen options that the particular options selected below...." For example, a MultipleCheck evaluator for the correct response to the question above would read,

If the student has chosen exactly the options {4, 8} ...

You will want to use the "at least" and "partly overlap" options of MultipleCheck, not necessarily the "exactly" option, when you write evaluators for wrong answers. For example, suppose you want to write particular feedback for when the student chooses F. You should use,

If the student has chosen at least the option {1} ...

because the student will have chosen not only option 1, but also one of options 5–8 from the second menu. If you want to write particular feedback for when the student cites basicity as a reason for increased nucleophilicity, you should use,

If the student has chosen options that only partly overlap the options {5, 6} ...

because the student cannot choose both 5 and 6, and the student must also choose one of options 1–4.

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Numeric and text questions

In a numeric question, a student enters a number. The question author can choose to specify whether a response should use scientific notation; if so, then the student enters the coefficient and the exponent in separate boxes. The question author can also choose to enter one or more units as question data. If the author enters one unit, it appears as text on the question-authoring page next to the boxes where the student enters the numbers. If the author enters more than one unit, they appear on the question-authoring page as options in a pulldown menu.

Numeric questions may contain variables in the question statement; for example:

How many moles of glucose are in [[x1]] mL of a [[x2]] M solution of glucose?
The question author writes a series of
question data that contain lists of possible values that ACE may choose at random to substitute for each variable when a student first views the question. (Once ACE chooses that value, it stores it, so the student always sees the same value in the future.) Each value may take one of two forms: either an arithmetical value, or a word and an arithmetical value. In the latter case, ACE will substitute the word for xn in the question statement; ACE will use the arithmetical value in any NumberIs evaluator that refers to the same variable (see below).

ACE provides three evaluators for numeric questions:

In a text question, a student enters text. ACE provides three evaluators: TextContains, TextWordCount, and HumanReqd. TextContains warrants a word of caution: it uses simple string search algorithms, so it will not recognize common misspellings (e.g., "mehtyl") as equivalent to strings that the author has specified. Authors may use regular expressions to search for patterns as well.

Any response will satisfy HumanReqd. When ACE encounters this evaluator, it marks the response as needing an instructor to assign a grade. The instructor can see in the gradebook which responses he or she needs to grade. The instructor clicks on the student's name and uses alter to assign a grade. This evaluator can be used for free-response questions, which ACE is not yet capable of grading automatically. Top.


Complete-the-table questions

A complete-the-table question is a variation of a text or numeric question. Students must complete a table by entering text or numbers into the cells. If they enter numbers, the numbers may be integral, decimal, or in scientific notation (e.g., 1.25 × 10-9). ACE provides nine evaluators. TableCellTextCt, TableCellNumCt, TableTextVal, and TableNumVal evaluate the contents of specific cells or entire rows and columns; TableTextText, TableNumText, TableTextNum, and TableNumNum evaluate the contents of cells in one column when another column in the same row has a particular value; and TableDiff compares a student's entire response to a table completed by the author. These evaluators share many variables and methods with NumberIs and TextContains. TableDiff also calculates the grade that a response receives (from the percentage of response table cells that match those in the author's table).

Authors can set any of the complete-the-table evaluators except TableDiff to ignore empty cells, treat them as containing the empty string "", or treat them as cause for displaying an error message to the student. They can also choose to set any of the evaluators that assess text to ignore case, and they can set any of the evaluators that assess numbers to ignore cells that contain nonnumeric values, treat them as containing the value 0, or treat them as cause for displaying an error message to the student.

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Clickable image questions

In a clickable image question, a student clicks on an image (the first Figure in a question). ACE marks the spot with the × symbol in a color chosen by the author to contrast with the greatest part of the image (red is default). The author may allow the student to mark the image in more than one location, in which case ACE places numbers on the image instead of the × symbol. Furthermore, a student may enter text to appear in place of the default marks.

ACE provides five evaluators for clickable image questions.

In four of the five evaluators, the author defines the regions by drawing one or more rectangles, circles, or ellipses on the image. To draw a shape, the author must click twice on the image. In the case of rectangles, the two clicks define opposite corners of the rectangle; in the case of circles, the first click defines the center of the circle, and the second click defines its radius; and in the case of ellipses, the first click defines the center of the ellipse, and the second click defines the lengths of the major and minor axes (twice the vertical and horizontal distances from the ellipse center). The sides of rectangles and the axes of ellipses are always horizontal or vertical.

When authoring a clickable-image question, one often wants to draw the regions for a ClickHere evaluator, and then use those same regions for a ClickNumber or ClickText evaluator. To do so, duplicate the ClickHere evaluator and save it without changing it. Then open the duplicate evaluator for editing and change it to a ClickNumber or ClickText evaluator.

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Draw-vectors questions

In a draw-vectors question, a student draws vectors on an image (the first Figure in a question). ACE displays the length and angle of each vector.

ACE provides three evaluators for draw-vectors questions:

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Equations questions

In an equations question, a student writes one or more mathematical equations or expressions. If the student writes more than one, the author can test whether each is equivalent to the next one.

ACE provides five evaluators for equations questions:

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Sharing questions with other instructors

If you author a question from scratch, the question will be visible only to you and students in your courses. If you wish to share your newly authored questions with other instructors, you need to export them from the question bank. Instructions:

  1. Enter the question bank.
  2. From the pulldown menus, choose the topic and question set in which the questions that you wish to export reside; or, enter a question number in the text box, press Go, and then press Exit w/o saving.
  3. Check the box next to the question(s) you wish to export.
  4. Press Export selected.
  5. Choose a name for the file (the suggested one or another) and press Submit.
  6. Right-click (Mac users: control-click) on the link and download the file to your drive.

You will now have a zip file on your hard drive. (Don't let your system unzip the file automatically. If it does, either rezip it, or find the original zip file and discard the unzipped file or folder.) You can now share the zip file with other instructors, who can import the questions themselves. Instructions:

  1. Enter the question bank.
  2. From the pulldown menus, choose the topic and question set into which you wish to import the questions. Or, make your own question set: Choose the topic, click on the add button icon next to the question set selector, enter the requested information, and press Save.
  3. Press Import questions.
  4. Press Choose file, navigate to the location of the zip file on your hard drive, and press Choose (or whatever is the equivalent in your browser).
  5. Press Upload. A "please wait"-type message will appear.
  6. The browser message bar at the bottom of the window should say "Loading...". If it doesn't, or if nothing happens after a few seconds, refresh the browser window. If the browser asks you if you want to send a form again, press Send (or whatever is the equivalent in your browser).
  7. When the message appears that ACE has successfully imported the questions, press OK. The window will close, and the question set should refresh itself to show the imported questions. If it doesn't, press Question Bank and renavigate to the question set.

ACE will treat the imported questions as questions that have been newly authored by the instructor who imported them.