Wednesday, 6 July 2016

Calculating %EXS in RWM combined

The KS2 results are out (joy!) and we know the national RWM combined figure is 53% so obviously we now want to know how we compare. This is where the problems start. There are two mistakes people commonly make when working out this figure and they are the same mistakes that were made when we had L4 RWM:

1) take the lower of the three percentages for individual subjects.

This is the more forgivable of the two mistakes. If the percentages meeting the expected standard in reading, writing and maths are 69%, 72% and 77% then you take the lowest one (69%) as the combined figure. I get why people do this and sometimes this is correct but don't assume it is. It is certainly the case that your combined figure cannot be higher than the lowest of the three, but it can be a lot lower.

2) take the average of the three percentages for individual subjects.

This is a common mistake and one that needs to stop. You don't average percentages. Well, there are occasions when it could work but this really isn't one of them. 

Essentially, the combined figure is about Venn diagrams, the pupils that plot in the intersect of the three circles. Imagine you had 9 pupils and 3 pupils (33%) achieved the expected standard in each subject. Using the above methods your combined figure would be 33% RWM. But it could be 0% if we had discrete groups achieving the expected standard in each subject. The pupils that achieved it in maths, did not achieve it in reading and writing; those that achieved it in reading did not do so in maths and writing and so on. No pupils achieved all three and so none plot in the interect of the Venn diagram.

Imagine you are standing out on the playground on a winter's day and you note that some children are wearing hats, some are wearing gloves and some are wearing scarves. Some are wearing just one of the items, some are wearing two, and some are wearing all three. You would not calculate the percentage wearing all three items - hats, gloves and scarves - by working out the percentage wearing the individual items and averaging it. That would be nuts. You would simply count how many pupils were wearing all three items together. You could even draw a Venn diagram on the playground and get pupils to stand in the right parts of the circles. 

That is no different to our approach to calculating %EXS in RWM. You need the pupil level data: a spreadsheet with the names of the pupils and 3 columns for reading, writing and maths. Then just enter a Y or N according to whether or not they met the expected standard in each subject. When you're done, count the number of pupils that have a Y in all 3 columns and divide that figure by the total number of pupils to get the correct percentage. 

Or if you're feeling flash, write a clever =IF formula in excel to do it all for you. I do love an =IF formula.

Hopefully that all makes some sort of sense.

10 comments:

  1. I mastered a combination of IF and AND formulas for this very purpose this year.
    #ExcelPride

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  2. Excellent. I love IF and AND. I have to show you the formula I used to work out possible APS score combinations for KS1 using new calculation. Found formula on Internet. It's nuts.

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  3. Hello,

    When calculating RWM is it the TANonAccountable or TAAcc that should be used for Writing?

    Thanks

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  4. I have no idea. What's the difference between the data in the two columns? I looked at the data collection guidance and can't find anything in there. Where is that data from?

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  5. I would have thought the 2nd one but not heard of this before. Let me know source and I'll ask a couple of people.

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  6. Hello,

    This data is in the download from the NCA Tools website for our prospective Year 7's next year. For the row 'E' it has both TANonAccountable and TAAcc with codes in.

    We have some students who have HNM in TANonAccountable and EXS in TAAcc. So I'm quite confused!

    Thanks for your help, I can't find anything anywhere!

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  7. Ah! Think we're getting there. Didn't realise this is secondary data. Also thought we were talking about writing; HNM doesn't apply to writing. So, it's possible that a pupils has a TA of HNM but passed the test (got a score above 100+) so the TA is overridden by EXS. Or vice versa: it's possible that a pupil was given a TA of EXS but scored below 100 in the test so the pupil is stated as HNM (has not met). I'm assuming that in the case of writing the data in both columns is the same?

    Best cross reference with the test scaled scores. The test score is king and defines your baseline. I assume that the TAAcc column.

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  8. Believe it or not, schools had to submit TA for reading and maths before having tests scores to guide them so could give HNM only for pupil to pass the test, or give EXS only for pupil to fail it. Complete waste of time. It would have been helpful if primary schools had access to the Tardis for this exercise so they knew the test score before making the assessment. There really was no point making the TA except for those below level of test because the test score rules.

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