Lower cut off score?
Posted: Mon Oct 21, 2013 8:40 pm
Does anyone have any idea what the new cut off scores are likely to be for the Grammar schools in Birmingham?
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Hmmmm what's that I can smell? Its the sweet smell of statistics in the morning!!KenR wrote:Actually that not correct - you can work it out based on the previous years average standardisation scores (shown under the scores in the sticky) - assuming only small changes in the number of candidates taking the exam
I did the calculation for KE-Ways as an example
For last year - the KE-Ways last candidate score was 227 with an average Std score of 114
114 is the 82nd percentile - so the top 18% candidates were successful out of 100%
This is equivalent to a probability of 1:5.55555
Increasing the year-7 entry from 150 to 180 will have an inverse effect on the success ratio in proportion to the increase.
This will have the effect of increasing the probability of success to 1:4.629629
Which is the equivalent of the 78.4 percentile
In terms of standardisation tables, 113 is the 80th percentile and 112 the 78th percentile. But closer to 112 in this case.
So assuming:-
(a) the cohort numbers remain unchanged from last year, and
(b) the distribution profile of choices by parents is similar to last year (both big assumptions)
We would predict the KE 5-Ways pass mark for the last successful candidate to drop from 227 to 224 if they increase the PAN from 150 to 180
Hope this helps
(The mathematical or statistically minded amount you can work this out for the other schools I hope)
So FW prediction is 224 (I understand it to be approximate)KenR wrote:Actually that not correct - you can work it out based on the previous years average standardisation scores (shown under the scores in the sticky) - assuming only small changes in the number of candidates taking the exam
I did the calculation for KE-Ways as an example
For last year - the KE-Ways last candidate score was 227 with an average Std score of 114
114 is the 82nd percentile - so the top 18% candidates were successful out of 100%
This is equivalent to a probability of 1:5.55555
Increasing the year-7 entry from 150 to 180 will have an inverse effect on the success ratio in proportion to the increase.
This will have the effect of increasing the probability of success to 1:4.629629
Which is the equivalent of the 78.4 percentile
In terms of standardisation tables, 113 is the 80th percentile and 112 the 78th percentile. But closer to 112 in this case.
So assuming:-
(a) the cohort numbers remain unchanged from last year, and
(b) the distribution profile of choices by parents is similar to last year (both big assumptions)
We would predict the KE 5-Ways pass mark for the last successful candidate to drop from 227 to 224 if they increase the PAN from 150 to 180
Hope this helps
(The mathematical or statistically minded amount you can work this out for the other schools I hope)
For what it's worth, I did the calculation for KEHG as well and it looks as though the percentile drops from the 70th to the 62.5th - which by my calculations would mean the pass mark for the last successful candidate dropping from 216 to 210