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I am trying to determine the ability of my students to touch type.

I have data on their speed (in seconds) and their accuracy (number of errors). I also know the number of words in the test (50 words).

Eg. Name: Bob, Speed: 113s, Errors: 19

Eg. Name: Jane, Speed: 831s, Errors: 65

How do I create an index value that places the students with the higher speed and the higher accuracy with the highest index value and a sliding scale for students with lower speed and lower accuracy?

The index would also reflect situations where students are slow but accurate, or fast yet inaccurate.

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up vote 1 down vote accepted

When I took typing, the formula was (words per minute)-10(mistakes) for a 1-2 minute test. You can adjust the coefficient as you wish depending on whether you think speed or accuracy is more important. Presumably the errors scale with time, so the coefficient should go down as the test length increases.

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I like the idea, however my test was based on the number of words (50 words / 261 characters), rather than a time limit. Therefore, I don't have the words per minute. I probably should add that the test will not allow the student to proceed until they have typed in the next correct character. – Paul Jun 7 '12 at 0:39
@Paul: you can still either use 2000-time-a*errors or 20000/time-errors, for example – Ross Millikan Jun 7 '12 at 1:37
Ah, that makes sense! Thanks for your help. – Paul Jun 7 '12 at 2:09

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