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Q&A #356

Teachers' Lounge Discussion: Curving test scores

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From: RON

To: Teacher2Teacher Public Discussion
Date: 2003060217:22:37
Subject: Re: curving test scores

SEVERAL POINTS: THE PURPOSE OF CURVING A TEST IS NOT TO HELP THE STUDENTS TO ACHIEVE A HIGHER SCORE. THE IDEA IS TO HAVE A COMPARISON OF STUDENTS RELATIVE ACHIEVEMENTS TO EACH OTHER ( PREFERABLY IN A LARGE GROUP). THE ASSIGNMENT OF GRADES ( PERCENT, LETTER, ETC.) IS DETERMINED NOT ON AN PRESET SCALE, BUT ON A SCALE DETERMINED BY THE RESULTS OF THE TEST. THIS METHOD ALLOWS TESTING WITH A GROUP OF QUESTIONS WHICH HAVE NOT BEEN SHOWN TO BE STATISTICALLY VALID. THE BASIC PREMISE IS THAT THE RAW SCORES OBTAINED BY THE GROUP OF STUDENTS WILL FIT A NORMAL DISTRIBUTION ( BELL CURVE). THE MEAN AND STANDARD DEVIATION ARE COMPUTED AND THE RAW SCORES ARE THEN TRANSFORMED INTO STANDARD NORMAL RESULTS. IT IS THESE TRANSFORMED SCORES THAT ARE ASSIGNED A GRADE. THE IDEA THAT A CURVE ON A TEST SHOULD ONLY BE USED WHEN TEST RESULTS ARE BELOW THE DESIRED LEVEL IS ONE CREATED BY PEOPLE WHO WISH TO ARTIFICIALLY INFLATE THE GRADES OF STUDENTS. THIS MAKES STUDENTS APPEAR TO BE ACHIEVING AT A HIGHER LEVEL THAN IS ACTUALLY THE CASE. IF CURVING TEST RESULTS IS A PRACTICE TO BE USED, THEN ALL TESTS SHOULD BE CURVED. THIS CAN PRODUCE SOME UNDESIRED GRADING RESULTS FOR THOSE WHO THINK THAT GIVING HIGHER GRADES IS BENEFICIAL TO STUDENTS. FOR EXAMPLE, IF A TEST IS GIVEN AND THE MEAN SCORE IS 95/100, THEN THAT WOULD IMPLY THE AVERAGE STUDENT (OR "C" STUDENT) WOULD GET APPROXIMATELY THAT SCORE. NOT MANY EDUCATORS ARE WILLING TO GIVE A STUDENT A GRADE OF "C" FOR GETTING A SCORE OF 95/100 ON A TEST, BUT THAT IS PRECISELY WHAT SHOULD OCCUR IF CURVING TEST SCORES IS TO BE USED. OTHERWISE, IF THE GRADES ARE ONLY TO BE RAISED AND NOT TO BE LOWERED BY CURVING SCORES INSTEAD OF USING A PRESET SCALE, THE OVERALL EFFECT IS TO INFLATE STUDENTS GRADES BEYOND THEIR ACTUAL VALUE. PERHAPS SOMEONE AT YOUR SCHOOL HAS STUDIED STATISTICS AND COULD HELP WITH THE APPROPRIATE COMPUTATIONS. IF NOT, I SUGGEST SOME READING ON THE STANDARD NORMAL PROBABILITY DISTRIBUTION AND HOW TO MAKE TRANSFORMATIONS FROM OTHER NORMAL DISTRIBUTIONS. THE COMPUTATIONS ARE NOT VERY DIFFICULT AND SEVERAL HAND HELD CALCULATORS HAVE PREPROGRAMMED FUNCTIONS FOR EXACTLY THAT. ONE OTHER CONCERN IS THAT APPARENTLY ALL TEACHERS ARE NOT DEVOTING THE SAME AMOUNT OF TIME OR PRIORITY TO THE SAME ITEMS OF THE CURRICULUM. IF IT IS THE POLICY OF YOUR SCHOOL THAT ALL TEACHERS SHOULD TEACH THE SAME CURRICULUM FOR THE PURPOSE OF GIVING ALL STUDENTS THE SAME TESTS, THEN THE FACULTY NEEDS TO BE VERY DILIGENT IN FOLLOWING THE PROGRAM. OTHERWISE, AS YOU INDICATED, SOME STUDENTS WILL BE AT A DISADVANTAGE WHEN TEST TIME COMES AROUND.

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