 6.4 Student Responses and Grading - Maple T.A. 2016 Help Instructor
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This section provides detailed information related to grading of student responses.

Student Responses

On an assignment, students can opt to enter their responses in Text Mode or Symbol Mode. The system default is Text Mode, in which students enter symbolic or numeric math expressions in simple keyboard notation, much like a graphing calculator. Symbol Mode allows students to enter responses using the Equation Editor. This setting applies to any question type that supports both modes. See Figure 6.1 and Figure 6.2. Figure 6.1: Students Can Change Entry Mode for Responses Figure 6.2: Students Can Use the Equation Editor for Responses

For other question types, a specialized input field is presented to the students. For more information on the input field for a specific question type, see the section on that question type in Authoring Question Types. For Maple syntax questions, the instructor specifies Symbol mode or Text mode for responses in the question itself. For more information, see Maple-graded Questions.

Controlling Answer Format in Numeric Questions

 Note: You can use the Question Editor's on-screen dialog boxes to set the answer format. For more information, see Setting the Answer Format in Numeric Questions.

Student responses do not need to be formatted identically to your answer to be correct. You can specify notations that the student is allowed to use.

Number Style

Use the numStyle field to set the acceptable formatting for student responses. List the acceptable number styles (in a space-separated list) as the value.

The available number styles are:

• thousands - responses containing commas (,) as a separator are graded correct
• scientific - responses specified using scientific notation, for example, 2.0E2, are graded correct
• dollars - responses containing a leading dollar sign (\$) are graded correct
• arithmetic - responses specified using the arithmetic operators, that is, +, -, *, /, (), and ^, are graded correct

For example:

numStyle = thousands dollars@

allows students to correctly enter responses using commas (,) separators or leading dollar signs (\$).

Negative Number Style

Use the negStyle field to set the acceptable formatting for negative student responses. Set negStyle to one of minus, paren, or both.

• minus - Negative responses must be entered using a negative sign (-).
• paren - Negative responses must be entered using parentheses (()).
• both - Negative responses can be entered using a negative sign (-) or parentheses (()). Note: If you set numStyle to include arithmetic, then you cannot allow parentheses to be used to indicate a negative response. That is, negStyle must be set to minus.

Numeric Questions

Setting the Answer Format in Numeric Questions

There is not general agreement on how to grade numeric answers with respect to the number of significant digits. For example, if the correct answer to 3 significant digits is 2.77, some instructors grade the response 2.77021 incorrect. Other instructors grade 2.77021 correct because they think that the inclusion of extra digits does not make a response incorrect.

In Maple T.A. you control how numeric responses are graded. For example, you can:

• Accept only 2.77 (and not 2.77021). For more information, see Setting the Precision.
• Accept all answers that agree with the correct answer to 3 (or another positive integer) significant figures (that is, any response between 2.765 and 2.775 is correct). For more information, see Setting a Margin of Error.

For Maple-graded questions, see Significant Digits in Maple Questions.

Setting the Precision

For the numeric question type, you can specify that the student response exactly match the correct answer, or specify that in addition to matching the value of your correct answer the student response have a specified number of significant digits.

Student responses that are correct up to the specified number of significant digits receive 50% credit.

For information on setting the precision for a numeric question, see Setting the Answer Tolerance in Numeric Questions.

For other formula questions, unless a margin of error is specified, the value of the student response must match that of the correct answer up to the tolerance specified by the tolerance field, which is by default is the system floating-point limit, 1.0E-9.

Setting a Margin of Error

You can specify a margin of error in one of two ways:

• Percentage: ± x%. This requires the student response to be within a specified percentage of the correct answer.
• Absolute: ± x. This requires the student response to be within a specified number of the correct answer.

For information on setting a margin of error for a numeric question, see Setting the Answer Tolerance in Numeric Questions.

For information on setting a margin of error for other question types, see Setting a Margin of Error in Non-numeric Questions.

 Note: It is recommended that you develop a policy for the tolerance in responses at the beginning of a project, so that every numeric question uses similar policies.

Tutorial: Setting Margin of Tolerance in Non-numeric Questions

lsu(n, x)

decimal(n, x), sig(n, x), int(x)

Setting a Margin of Error in Non-numeric Questions

 Note: Use the Question Editor's on-screen dialog boxes for setting the margin of error in numeric and numeric-with-unit questions. For more information, see Setting the Answer Format in Numeric Questions.

For an introduction to the concept of margin of error, see Controlling Answer Tolerance.

The exact answer is not always required. In Maple T.A., you can specify a margin of error, within which student responses are graded correct, for any mathematical question type. You can specify a margin of error for answers that are static or defined using algorithmic variables.

Use "?" in the answer field to set a margin of error. The ? (plus or minus) operator represents "+/-" in ordinary math notation. You can specify an absolute tolerance. For example, to accept 2.5 +/- 0.25, that is, any response between 2.25 and 2.75 (inclusive), use 2.5 ? 0.25. You can also specify a percentage tolerance. To accept 5.12 +/- 5%, that is, any response between 4.864 and 5.376 (inclusive), use 5.12(1 ? 0.05).

 Note: The ? operator cannot be used in an algorithmic variable definition (or other algorithmic statement).

For numeric and Maple-graded questions, you cannot use the "?" operator. For information on specifying a margin of error for a numeric question, see Setting the Answer Tolerance in Numeric Questions. To specify a margin of error in a Maple-graded question, use Maple code.

Consider the following when working with margins of error:

• Precedence of the ? Operator: The ? operator is of the same precedence as "+" and "-". For example, 2*3 ? 0.5 is the same as 6 ? 0.5 and 2*(3 ? 0.5) is the same as 6 ? 1.

• Units: Because expressions with units have different dimensions from pure numbers, you must specify a dimensioned margin of error for a dimensioned answer. To specify "2kg with a tolerance of 0.1kg", enter 2kg ? 0.1kg or (2 ? 0.1)kg. To specify "50cm within 5%", enter (1 ? 0.05)50cm.

 Important: The expression 50cm ? 2 is invalid. It is a mixed expression. The left-hand side has dimension length. The right-hand side is dimensionless (a pure number).

• The ? operator is not available to students: A student cannot specify a margin of error. The above issues do not arise for students.

For more examples and information, see Tutorial: Setting Margin of Tolerance in Non-numeric Questions.

Significant Digits in Maple Questions

The Maple Digits environment variable controls the number of digits that Maple uses when calculating with software floating-point numbers.

• The default value of Digits is 10.
• The value of Digits is changed by using the assignment operator. For example, Digits:= 20;

Using the evalf Command to Set the Value of the Digits Variable

The parameter n, which can be given as a second argument (evalf(expr, n)), sets the value of Digits for a single computation.

To round the exact answer, assign the exact answer to a dummy variable, and then use the evalf(expr,n) command in the evalb command to compare the student response to the rounded answer.

Example

Calculate the quadratic mean of the following list of data: [695, 607, 511, 588, 710, 500, 682, 515, 709, 478, 497, 657, 652, 634, 488, 615, 714, 579, 589, 493, 584, 484, 503, 711, 622, 695]. The answer requires 5 significant digits.

1. First calculate the exact numeric answer.
1. Round it to the required number of significant digits. For example:

```exact_answer:=evalf(Statistics[Mean](<695, 607,  511, 588, 710, 500, 682, 515, 709, 478, 497, 657, 652, 634, 488, 615,  714, 579, 589, 493, 584, 484, 503, 711, 622, 695>)):
```

Using Maple Code to Prevent Cheating in Maple Syntax Questions

As the author, you can verify whether a student is using a Maple command to calculate the answer.

The following example scripts illustrate code that allows and prevents potential cheating by the student using Maple commands.

Examples

The student is required to factor(x^2-1). The expected correct response is (x-1)*(x+1).

In this example question code, the student could easily use the Maple factor command to obtain the answer.

```question=Factor x^2-1.@
maple=evalb(\$RESPONSE=factor(x^2-1))@
type=maple@
mode=Maple@
allow2d=0@
name=Allow Cheating@
editing=useHTML@
```

In this example, the code verifies if the factor command has been used in the answer. The student response will be marked incorrect if the Maple factor command is used.

```question=Factor(x^2-1)@
maple=evalb(0=StringTools[Search]("factor","\$RESPONSE")) and evalb(\$RESPONSE=factor(x^2-1))@
type=maple@
mode=Maple@
allow2d=0@
name=Prevent Cheating@
editing=useHTML@
```

If you are concerned about students using Maple commands to calculate answers, consider using Maple-graded Formula to create your question. Students respond with a limited number of expressions and functions. As such, you do not need to explicitly check that the student response is a Maple command. For details, see the Syntax and Student Response subsections of Maple-graded Formula.

Maple Syntax

Entering Chemistry Expressions

There are two ways to enter the answer to a question of the chemistry question type.

Text Mode

The system default mode is Text Mode, in which you enter symbolic or numeric math expressions in a simple keyboard notation, much like a graphing calculator.

Table 6.1: Guidelines for Entering Chemistry Expressions

Rule

Examples

Superscripts and Subscripts

Enter superscripts using the caret "^" character, and subscripts using the underscore "_".

H_2O H_2SO_4 Arrows in Equations

Use the text ->, <-, <=> for arrows.

-> <- <=> Other Operators

Use "*" for the center dot operator.

* + Note: No other operations are allowed in equations. You can use the "-" sign to indicate ion charges (see below.)

Physical States, Ion charges, and Parentheses

Be sure to include physical states (in parentheses) if your equation requires them.

Use the "+" and "-" characters for polarity and ion charges.

Use parentheses to clarify interpretation of groups of characters.

Ca^2+(aq)+ (CO_3)^2- (aq) -> CaCO_3 (s) Symbol Mode

For chemistry formula questions, you can also use Symbol Mode entry, which allows you to enter formulas in a WYSIWYG ("What you see is what you get") editing window. You can pick arrows, symbols or operators from a palette, and see your expressions appear as you type. Select Equation Editor in the Edit Question window of the Mathematical Formula question type to display the symbol palette.

Rules for Chemistry Expressions and Equations

• Spaces are ignored in expressions.
• Parentheses may be used to clarify physical states, compound groupings, and application of ion charges. Use the formula preview link to preview your expressions.
• In grading equations, any characters you enclose in parentheses (for example, ion charges, superscripts, subscripts, etc.) are associated with the preceding term (not the next term). Example: Pb^(2+) is Pb2+
• For numbers that are not super or subscripted that precede a compound or element, the grader associates the number with the term that follows. Example: 2H_2O is 2H2O

Chemical Equation Subtype

Plotting a Student Response

Maple T.A. uses Maple plotting features to graph student responses or a function derived from a student response, for example, the definite integral of the student response. Maple provides many ways of representing data and mathematical expressions graphically using plots.

Plotting a student response is available only with the Maple-graded question type.

Plotting a Student Response

When entering code for plotting in the Question Editor, use only one Maple plot command. It must be the last command entered. You must use the long form name for Maple package functions.

Example

The following is the source file for a Maple-graded Formula question that plots the student response.

```question=Enter an expression in x@
maple=true@
plot=plot(\$RESPONSE,x=0..10)@
type=formula@
mode=Maple@
name=2D Maple plot@
editing=useHTML@```

The following is the source code for a Maple Syntax question that plots the student response using the Maple tubeplot command. Students must use Maple syntax in their response.

```question=Enter a set of spacecurves using Maple syntax, for example, [cos(t),sin(t),0]@
maple=true@