z-scores

z-scores

by Steve Towson -
Number of replies: 12

Our students need to know the following information when they look at their grades - the percentage mark, the class average, the mean of the class and the z-score (standard score).

The z-score is

z = {x- \mu \over \sigma}

where:

x is a raw score to be standardized;
μ is the mean of the population;
σ is the standard deviation of the population.

The quantity z represents the distance between the raw score and the population mean in units of the standard deviation. z is negative when the raw score is below the mean, positive when above.

Is there anyway that we can have this information displayed for each student when they view their grades?

Thanks in advance.

In reply to Steve Towson

Re: z-scores

by Elena Ivanova -

the answer will be - if you develop a code yourself
(not sure how helpful this is blush)

In reply to Elena Ivanova

Re: z-scores

by Steve Towson -

No, not particularly helpful.  If I could do it myself I wouldn't be asking other people.  I'd  be doing it and then posting the how to here.

In reply to Steve Towson

Re: z-scores

by Elena Ivanova -

hmmm, people often think that there are tricks in the user interface to do things. Sometimes there are, sometimes there are not.
I assumed that you are asking about the user interface, and that is why I told you that one cannot do that there.
Hopefully somebody else will be able to help you. If you will not get an aswer, then you can probably also ask in the Development forum later.

In reply to Steve Towson

Re: z-scores

by Mauno Korpelainen -

In Finland our students get standardized grades only in very big nation-wide or international tests and as a math teacher I find it very hard to understand why some countries/teachers use z-scores because distributions of grades/scores of typical classes/students/tests of moodle are not usually normal (bell-curves). Is it after all so important to know your relative performance to others in the class - if you were worse or better than others - grading is relative in any case depending on scales and questions that teachers select.

I suppose you could export grades to Excel, count mean of population and standard deviation of population and z-scores in Excel and give students that z-score in Grade Feedback so that each student sees only his/her own z-score. Or you could check the grade report as a teacher and tell personally to each student that they succeeded better or worse than average moodlers in those tests. wink

In reply to Mauno Korpelainen

Re: z-scores

by Steve Towson -

Personally I agree, but ... it's a legal requirement for us to give the students this information.  Can anyone give me a hint where I could start modifying the code?

In reply to Steve Towson

Re: z-scores

by Bob Puffer -

Currently the user report doesn't calc averages though you can take a look at MDL-20617 which are code changes (ostensibly to core, we hope) that include average going to the user report.  Most changes are in grade/report/user/lib.php in function fill_table_recursive, likely the same place where you'd need to make changes to accommodate your special needs.  I might mention that you're correct in identifying that the major challenge of hacking the gradebook lies in knowing where, the how is relatively easy.

In reply to Steve Towson

Re: z-scores

by Marc Grober -
I would obliged if you could provide the cite to WA statute or regulation that mandated reporting z-scores to students. I had heard that WA was somewhat backward when it came to it's Education Department, but had no idea things were this bad.......
In reply to Marc Grober

Re: z-scores

by Steve Towson -

WA isn't that bad.  I'm now working in the ACT - we have to post a spreadsheet on the noticeboard with anonymous student grades after each task, ranked, with the student's z-score and task average clearly identified.

In reply to Steve Towson

Re: z-scores

by Marc Grober -
It might actually be worthwhile to use the google API to fill a google spreadsheet with data from your Moodle DB, and use the statistical features available to produce the doc you want to post. That way you can also include charts to facilitate explanation of the z-score (I dont't imagine too many HS students in US have any idea what standard deviation is about-lol)
In reply to Mauno Korpelainen

Re: z-scores

by Marc Grober -
Unfortunately, Mauno, in the US a score, no matter how meaningless, is often the hallmark of education.
In reply to Mauno Korpelainen

Re: z-scores

by Gary Anderson -

There is the ability to enable "rank" (which is off by default) for the site and within each course which gives the student the ability to see how they stand on either any given activity or the whole course.   This would probably be useful in the case where scores are not normally distributed.

The gradebook does have the ability for developers to write new reports; one with the z-score might be useful.  Although for myself, this seems a simple enough task to export to a spreadsheet and post the results if such a report is desired and it gives the teacher the ability to put these numbers in context which would seem to be important for many students to correctly evaluate their performance.

In reply to Gary Anderson

Re: z-scores

by H Singh -

I wonder if anyone has written a tool for computing the z-score and including it in reporting.

I want to actually go further and grade on the basis of the z-score, but a start would be useful.

I am utterly new to coding for Moodle, but will have to learn I guess.