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Using Power Law to Calculate Student Performance for a Competency

This topic describes the best practices and prerequisites for using the Power Law accumulator type to calculate student performance. For more information on how the Power Law accumulator compares to the other available accumulators, refer to Calculate Competency Marks Using Standards-Based Gradebook on page 1.

Best practices for using power law to calculate student scores for a competency

  • The competency should be measured at least 3 times within a marking period that a mark is reported, and it should be measured at consistent intervals.
  • Assignment scores should be entered based on a score scale that reflects student performance (e.g. Advanced, Proficient, Basic, Below Basic). The following 4-point scale is an example of scores that would be entered for each assignment.

    Below Basic


  • The formula is best used on a narrowly defined competency where you know that you are measuring the same skill each time the student is assessed
  • The Power Law accumulator type returns the student's mark that is an estimate of the student's true score while other accumulator types return a mark based on a calculated percentage correct. Having a competency group which uses power law for some competencies and another accumulator type for other competencies may confuse teachers.
  • If the student's performance for multiple competencies will be averaged to determine a student's performance for an overall competency, and one of these competencies uses the Power Law accumulator type then all competencies under the overall competency should use it and should use the same score scale. For example, if a Reading competency is calculated based on the student's performance in Word Recognition and Vocabulary, Reading for Main Idea, and Comprehension competencies and you want to use power law to calculate performance for any of the competencies, then all of these competencies should use the Power Law accumulator type.

Prerequisites for using power law

  1. Determine the score scale that will be used for all assignments that will be associated with the competency. For example, you could use a scale of 1 (Beginning work on standard), 2 (Progressing toward standard), 3 (Approaching standard), and 4 (Meeting standard).
  2. Define a Competency Grading Scale to return a mark based on the score scale you are using. For example, if a score of 3.5 or higher should result in student receiving a 4 (Meeting standards), enter 3.5 in the Minimum Percent field on the Competency Grading Scale page.
  3. Set the Accumulator Type to Power Law and the Grading Scale to your Power Law grading scale on the Competency Setup page for the competencies that will be calculated using the power law.
  4. Inform teachers that assignments for the competency must be scored using the score scale.
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