pl-checkbox element

A pl-checkbox element displays a subset of the answers in a random order as checkboxes.

Sample element

question.html

<pl-checkbox answers-name="vpos" weight="1">
  <pl-answer correct="true">A-B</pl-answer>
  <pl-answer correct="true">B-C</pl-answer>
  <pl-answer> C-D</pl-answer>
  <pl-answer correct="true">D-E</pl-answer>
  <pl-answer> E-F</pl-answer>
  <pl-answer> F-G</pl-answer>
</pl-checkbox>

Customizations

Attribute	Type	Default	Description
answers-name	string	—	Variable name to store data in. Note that this attribute has to be unique within a question, i.e., no value for this attribute should be repeated within a question.
detailed-help-text	boolean	false	Display the minimum and maximum number of options that can be selected in a valid submission. See explanation below.
display	string	"block"	How to display answer choices: "block" (separate lines) or "inline" (single line).
hide-answer-panel	boolean	false	Option to not display the correct answer in the correct panel.
hide-help-text	boolean	false	Help text with hint regarding the selection of answers. Popover button describes the selected grading algorithm ("off", "coverage", "each-answer", or "net-correct").
hide-letter-keys	boolean	false	Hide the letter keys in the answer list, i.e., (a), (b), (c), etc.
hide-score-badge	boolean	false	Hide badges next to selected answers.
max-correct	integer	See description	The maximum number of correct answers to display. Defaults to displaying all correct answers.
max-select	integer	See description	The maximum number of answers that can be selected in any valid submission. Defaults to max-correct if that attribute is specified along with detailed-help-text="true"; otherwise, defaults to the number of displayed answers.
min-correct	integer	See description	The minimum number of correct answers to display. Defaults to displaying all correct answers.
min-select	integer	See description	The minimum number of answers that must be selected in any valid submission. Defaults to min-correct if that attribute is specified along with detailed-help-text="true"; otherwise, defaults to 1.
number-answers	integer	See description	The total number of answer choices to display. Defaults to displaying all answers.
order	string	"random"	Order of answer choices: "random" (randomized) or "fixed" (as written).
partial-credit	string	"off"	Grading method: "off" (all-or-nothing, default), "net-correct", "coverage", or "each-answer".
show-number-correct	boolean	false	Display the number of correct choices in the help text.
weight	integer	1	Weight to use when computing a weighted average score over elements.

Inside the pl-checkbox element, each choice must be specified with a pl-answer that has attributes:

Attribute	Type	Default	Description
correct	boolean	false	Is this a correct answer to the question?
feedback	string	—	Helper text (HTML) to be displayed to the student next to the option after question is graded if this option has been selected by the student.

Partial credit grading

Four grading methods are available using the partial-credit attribute:

• "off" (All-or-nothing, default): Students receive full credit only if they select all correct answers and no incorrect answers. Otherwise, they receive zero credit.

• "net-correct" (Net Correct): 1 point is added for each correct answer that is marked as correct and 1 point is subtracted for each incorrect answer that is marked as correct. The final score is the resulting summation of points divided by the total number of correct answers. The minimum final score is set to zero.

• "coverage" (Coverage): The final score is calculated by multiplying the base score (the proportion of correct answers that are chosen) with the guessing factor (the proportion of chosen answers that are correct). Specifically, if t is the number of correct answers chosen, c is the total number of correct answers, and n is the total number of answers chosen, then the final score is (t / c) * (t / n). This grading scheme rewards submissions that include (i.e. "cover") all true options.

• "each-answer" (Every Decision Counts): The checkbox answers are considered as a list of true/false answers. If n is the total number of answers, each answer is assigned 1/n points. The total score is the summation of the points for every correct answer selected and every incorrect answer left unselected.

Migrating from deprecated attributes

The following deprecated attributes are still supported for backward compatibility:

Old syntax	New syntax
partial-credit="false"	partial-credit="off"
partial-credit="true"	partial-credit="net-correct"
partial-credit="true" partial-credit-method="EDC"	partial-credit="each-answer"
partial-credit="true" partial-credit-method="COV"	partial-credit="coverage"
inline="true"	display="inline"
fixed-order="true"	order="fixed"

Using the detailed-help-text attribute

The detailed-help-text attribute can be used with min-correct and/or max-correct to help students select the correct options. If min-select is not specified, then setting detailed-help-text="true" ensures that the number of selected options in a valid submission is at least the value of min-correct. Similarly, if max-select is not specified, then setting detailed-help-text="true" ensures that the number of selected options in a valid submission is at most the value of max-correct. For example, if a checkbox question does not specify min-select or max-select, and specifies min-correct="2", max-correct="4", and detailed-help-text="true", then all valid submissions must select between 2 and 4 options. Thus, we help students by preventing them from selecting, say, five options. Indeed, if five options are selected, then at least one selected option is incorrect since there are at most four correct options.

Note that explicitly specifying min-select overrides the minimum number of options that must be selected, and similarly, explicitly specifying max-select overrides the maximum number of options that can be selected.

Restricting the number of options that can be selected

The min-select and max-select attributes determine the minimum and maximum number of options that can be selected in a valid submission. The value of min-select is computed using the following steps:

1. If the min-select attribute is explicitly set, then we use the specified value of min-select.
2. If min-select is not specified, but min-correct is specified along with detailed-help-text="true", then we use the specified value of min-correct.
3. If steps 1 and 2 do not apply, then we use a default value of 1.

To compute max-select, we use a similar algorithm (note the different default value in step 3):

1. If the max-select attribute is explicitly set, then we use the specified value of max-select.
2. If max-select is not specified, but max-correct is specified along with detailed-help-text="true", then we use the specified value of max-correct.
3. If steps 1 and 2 do not apply, then max-select defaults to the number of displayed checkbox options (i.e. students can select all displayed options by default).

Example implementations

• element/checkbox
• demo/randomCheckbox

See also

• pl-multiple-choice for allowing only one correct choice

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