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  • Grading criteria for simple allowable error

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    • Setting Grading criteria up for relative and absolute error

      Unless you want adaptive marking or composite answers in one part, just use the non-expert mode of error - it's much more stable. 

      To do this, select either relative or absolute error and set the level.  
        • Moodle reads relative error as a percentage (a relative error of <0.01 means the error must be less than 1% of the answer). If the correct answer is 100, say, the student's answer has to be within 1% of 100, or between 99 and 101.
        • Moodle reads absolute error as an actual number. Therefore, an absolute error of <1 means the error must be within 1 integer of the answer. If the correct answer is 7, then the student answer has to be between 6 and 8. Absolute error is more suited to money questions or when the answer is fixed (not using random variables). 

      If you don't want any allowable error at all, set the relative error to 0 (relerr == 0). However, beware of possible snags if you are using numbers with large decimals and student rounding in the question.  If your answer will result in a large or infinite number of decimal places (e.g., usually division), you cannot set absolute error == 0, as Moodle will mark the question incorrect, even if the computer-generated correct answer is entered.


      Things to watch out for:

      1. The error settings within Moodle are sometimes unstable. If possible, use the error settings in simple mode, as these seem to be more robust. 
      2. You need to set the error so that it will cover ambiguities due to long decimal places and rounding off.
      3. You cannot set different errors for composite  answers in the same part. Further, if you have a question with composite answers in the same part, Moodle will take the error you set, work it out for the largest/highest answer, and than apply that error to all of the other answers. Moodle will not calculate a different error for each answer.
      4. Once you've set up the question, it's critical that you double-check that the settings are working correctly by previewing and testing different answers.  Make sure that Moodle isn’t allowing larger percentages than you’ve set (for example, allowing errors of up to 2% even though the setting is for 1%.) 


      Note for advanced users: You can also use minimum and maximum operators for setting error in the grading criteria:

        • errormin = _relerr < 0.01
        • errormax = _relerr < 0.1

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