Rounding Error or not?

Asked by Andrew Richards on 2014-01-23

Hi everyone

I recently updated my Schooltool installation and I am not sure whether this error has been introduced or if the function was not available in the first instance.

I was printing off a worksheet for this week's Year 8 parent's evening and noticed that the grade average for one student was 79.8% but the displayed grade on my term report was a 'B'. On my customised scoring system, the pass score for 'A' is 80%. Therefore, I would have expected the system to round-up the percentage average when displaying the grade. I usually display the grade view when adding activity scores to the worksheet. The worksheet did have weighting applied so I don't know whether may have been a factor as well.

It would also be nice to see both the average % score and the equivalent grade value displayed in the same worksheet view.

Any thoughts?
Andy R

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Tom Hoffman (tom-hoffman) said : #1

We'll check the code and get back to you. It is definitely something where different people might have different expectations. I also see your point about having a column for both.

Andrew Richards (arichards-p) said : #2

Hi Tim,

I have checked through my worksheets for other groups and get the same problem. I have a sneaking suspicion that the scoring algorithm for SchoolTool does not round up the average grade to a full integer since it may be based upon the US GPA marking system, where many schools use a two point decimal system to give a finalised GPA score average.

This of course makes it difficult to create accurate end of term reports from the system, and I don't fancy creating custom reports from scratch. Not enough experience with report markup language or ZODB/ZOPE.

Andy R

Tom Hoffman (tom-hoffman) said : #3

Hm... Well, one workaround would be to make a scoresystem that made 79.5% the cutoff? 79.45%?

I'm not sure the current implementation reflects as much thought as you are reading into it. We'll go over it again.

Gediminas Paulauskas (menesis) said : #4

To find an appropriate score, the average is compared to score's 'low percentage' until a too big one is found. The average is not rounded before doing so. 79.8% is less than 80%. Even a 79.99% average, that would be displayed as 80.0% with "No score system" selected, would still be converted to a B.

It is not a rounding error, because no rounding is being done... But clearly, you expect it to be rounded to a whole number.

Yes, a score system that uses 79.5 as cutoff would behave as if the result was rounded.

Calculations differ when category weights are used or not, but it does not matter for this question.

I have no opinion which behaviour is correct, expected, or more intuitive. This is only an explanation.

Tom Hoffman (tom-hoffman) said : #5

It is kind of a toss up, because I'd say not rounding is more "correct," but most teachers probably do round.

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