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Julian Arni
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docs/data/source/course_data_formats/grading.rst
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docs/data/source/course_data_formats/grading.rst
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##############
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Course Grading
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##############
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This document is written to help professors understand how a final grade for a
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course is computed.
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Course grading is the process of taking all of the problems scores for a student
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in a course and generating a final score (and corresponding letter grade). This
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grading process can be split into two phases - totaling sections and section
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weighting.
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*****************
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Totaling sections
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*****************
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The process of totaling sections is to get a percentage score (between 0.0 and
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1.0) for every section in the course. A section is any module that is a direct
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child of a chapter. For example, psets, labs, and sequences are all common
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sections. Only the *percentage* on the section will be available to compute the
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final grade, *not* the final number of points earned / possible.
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.. important::
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For a section to be included in the final grade, the policies file must set
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`graded = True` for the section.
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For each section, the grading function retrieves all problems within the
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section. The section percentage is computed as (total points earned) / (total
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points possible).
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******************
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Weighting Problems
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******************
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In some cases, one might want to give weights to problems within a section. For
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example, a final exam might contain four questions each worth 1 point by default.
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This means each question would by default have the same weight. If one wanted
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the first problem to be worth 50% of the final exam, the policy file could specify
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weights of 30, 10, 10, and 10 to the four problems, respectively.
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Note that the default weight of a problem **is not 1**. The default weight of a
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problem is the module's `max_grade`.
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If weighting is set, each problem is worth the number of points assigned, regardless of the number of responses it contains.
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Consider a Homework section that contains two problems.
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.. code-block:: xml
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<problem display_name=”Problem 1”>
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<numericalresponse> ... </numericalreponse>
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</problem>
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.. code-block:: xml
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<problem display_name=”Problem 2”>
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<numericalresponse> ... </numericalreponse>
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<numericalresponse> ... </numericalreponse>
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<numericalresponse> ... </numericalreponse>
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</problem>
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Without weighting, Problem 1 is worth 25% of the assignment, and Problem 2 is worth 75% of the assignment.
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Weighting for the problems can be set in the policy.json file.
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.. code-block:: json
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"problem/problem1": {
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"weight": 2
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},
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"problem/problem2": {
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"weight": 2
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},
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With the above weighting, Problems 1 and 2 are each worth 50% of the assignment.
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Please note: When problems have weight, the point value is automatically included in the display name *except* when `"weight": 1`. When the weight is 1, no visual change occurs in the display name, leaving the point value open to interpretation to the student.
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******************
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Weighting Sections
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******************
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Once each section has a percentage score, we must total those sections into a
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final grade. Of course, not every section has equal weight in the final grade.
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The policies for weighting sections into a final grade are specified in the
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grading_policy.json file.
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The `grading_policy.json` file specifies several sub-graders that are each given
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a weight and factored into the final grade. There are currently two types of
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sub-graders, section format graders and single section graders.
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We will use this simple example of a grader with one section format grader and
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one single section grader.
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.. code-block:: json
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"GRADER" : [
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{
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"type" : "Homework",
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"min_count" : 12,
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"drop_count" : 2,
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"short_label" : "HW",
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"weight" : 0.4
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},
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{
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"type" : "Final",
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"name" : "Final Exam",
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"short_label" : "Final",
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"weight" : 0.6
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}
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]
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Section Format Graders
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======================
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A section format grader grades a set of sections with the same format, as
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defined in the course policy file. To make a vertical named Homework1 be graded
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by the Homework section format grader, the following definition would be in the
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course policy file.
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.. code-block:: json
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"vertical/Homework1": {
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"display_name": "Homework 1",
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"graded": true,
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"format": "Homework"
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},
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In the example above, the section format grader declares that it will expect to
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find at least 12 sections with the format "Homework". It will drop the lowest 2.
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All of the homework assignments will have equal weight, relative to each other
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(except, of course, for the assignments that are dropped).
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This format supports forecasting the number of homework assignments. For
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example, if the course only has 3 homeworks written, but the section format
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grader has been told to expect 12, the missing 9 will have an assumed 0% and
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will still show up in the grade breakdown.
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A section format grader will also show the average of that section in the grade
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breakdown (shown on the Progress page, gradebook, etc.).
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Single Section Graders
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======================
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A single section grader grades exactly that - a single section. If a section
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is found with a matching format and display name then the score of that section
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is used. If not, a score of 0% is assumed.
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Combining sub-graders
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=====================
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The final grade is computed by taking the score and weight of each sub grader.
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In the above example, homework will be 40% of the final grade. The final exam
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will be 60% of the final grade.
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**************************
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Displaying the final grade
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**************************
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The final grade is then rounded up to the nearest percentage point. This is so
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the system can consistently display a percentage without worrying whether the
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displayed percentage has been rounded up or down (potentially misleading the
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student). The formula for the rounding is::
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rounded_percent = round(computed_percent * 100 + 0.05) / 100
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The grading policy file also specifies the cutoffs for the grade levels. A
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grade is either A, B, or C. If the student does not reach the cutoff threshold
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for a C grade then the student has not earned a grade and will not be eligible
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for a certificate. Letter grades are only awarded to students who have
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completed the course. There is no notion of a failing letter grade.
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