Nonsuch 2010 top 80 and in catchment cut-off scores

[stressedparent]

Hi to all,
Giulio have a look @ this and tell me what you think? You can make corrections if you wish.

I have spent few hours correlating this data from this web site and literature from the open evenings. To make the data accurate I have used Tiffin school final cut-off for last 3 years and Nonsuch last year results.

We know Tiffin offer 120 places and non such offer 80 places for ooc candidates.



Tiffin 2008, 987 girls sat the test. Initial cut-off 231which is on the 85.5 percentile

987*14.5/100 = 143 in rank, which means 23 girls, must have had other preferences and Tiffin was not their first choice. This is a percentage of 19% not choosing Tiffin.


Tiffin 2009 , 1002 girls sat test. Initial cut-off 233, which means they have offered to first 13.5%

1002*13.5/100 = 135 .2, 15 girls did not have Tiffin as first choice.

You can see, as the credit crunch started to bite the rank order is getting smaller as only 12.5% had other schools as first preference.

Tiffin 2010, 1170 girls sat the test. Initial offer 237, which means they offered to the 89.5 percentile. Your DD had to be in the top 10.5% to get a place on initial offers.

1170*10.5/100 =123 , 3 girls did not have Tiffin as first choice. Which explains why the Tiffin mark was high last year as less people went to private hence only 2.5% who sat test not choosing Tiffin.

Non such 2010 admission, 1288 sat test to be in top 80 you had to be in the top 6.21% Which is on the 93.7-percentile approx.

1288*6.21/100=80This equates to a standardised score of 245, this would have been the top 80 cut-off mark before the national offer day on 1st of March.


The actual Final cut off for top 80 was 237 which lies on the 89.5 percentile this equates to a rank order of 134.
237/2=118.5 standardised
1288*10.5/100= 135, this means 55 girls in the top 80 must had other first choices or only used the test as a mock test for other schools like Tiffin, Kendrick and Langley.

With all this information we could estimate what will be the cut-off mark for top 80 for 2011 as follows,

1390 sat test top 80 must be on the 94.2 percentile. Your DD must be in the top 5.8% 80/1390*100= 5.8 approx
Which equates to a standardised score of 248.

Lets assume 69% of top 80 girls decide to go somewhere else. 80+35= give a total of 135. so if you are on this rank there might be a good chance of ooc place. Rank 135 equates to 135/1390 =9.7 %. DD has to be on the 90.3 percentile this equates to a standardised score of 238.

Due to the high number taking the test and applying the data from Tiffin and nonesuch results from last year I assume the initial ooc cut off this year will be 238 give and take one mark. Of course these only calculations using assumptions to predict future cut-off scores. The big variable is the number of girls in the top 80 that decide to go somewhere else.

stressedparent

[2outof3]

I for one am dumbstruck! Even if your calculations are completely wrong, its still amazing that you even know where to start!

[sgcmum]

hi stressedparent,

based on previous years info i ended up with nearly the same cut off i.e 246 to be in top 80 and maybe 239/238 as cut off on offer day.
any similar workings for in catchment?

p.s these are rough workings only..just to help us in deciding whether or not to name the school in the c.a.f.
-done purely based on previous years' data-'ball park numbers' so to speak

sgcmum.

[stressedparent]

Hi sgcmum,

Many thanks for your input, 2011 cut-off for in catchments is hard to guesstimate as the relationship is no longer linear due to the fact that a lot of ooc candidates that score higher than in catchments but still will not get a place. But if we make further assumptions reference this sample" not getting a place" and apply the same data from last year and this year you will find the in catchments mark for this year will go up by nearly 3 standardised score to 215.

2010 admission year data, 212 was offered which is on the 66th percentile, which equates to the following rank,

1288*34/100= 437 offers to rank 437
2011 admission data 437/1390= 31 which means your DD will have to be in the top 31%. She has to be on the 69th percentile, which equates to 107.5*2 =215 standardised.

These are only predictions based on data from previous years; it is only been made to help us make our decision reference caf preference

So the initial cut-off for 2011 admission will be within the range 214-216 for in catchments and within the range of 237-239 for ooc.

stressedparent

[sensibility]

Wonderful work you all. The stress of waiting is not easing at all. I hope the cut off score for OOC girls drops a little lower for us cos we are so close to the predictions!

Thanks anyway

[runningmum]

What is particularly puzzling when interpreting the NFER table is that the top 50 % of the sample is arranged from 100 to 140 whilst the bottom 50 % is only arranged over a spread of 30. Can you interpret this stressed parent? I'm not sure of the range that Nonsuch uses, but assumed it would be even both sides of the mean (a range from 120 to 280), and that the top of the bell would be centred around a score of 200. Does anyone know the lowest possible score in the test?

[stressedparent]

Hi runningmum,

Nfer uses a range from 70 to 140, to Asses the data from the Nonsuch results you have to divide the score by 2, which gives a mean score of the combined scores. I have pasted a link to the NFER website for an explanation of the bell curve and how you should interpret the data.
http://www.nfer.ac.uk/nfer/research/ass" onclick="window.open(this.href);return false; ... scores.cfm.

stressedparent

[Giulio]

Hi stressedparent
yep, that is how would guess it, like in your posting at the top. That is how I work them out.
I would give or take a bit more. Having seen the nonsuch scores when they had top 50, and the Wallington girls scores, I think there must be other factors that influence the actual scores and pass marks.
Maybe the normalisation is not done just vs the population that sat the exam but against a national population, or maybe the difficulty of the test has an effect on the scores (but not on the ranking).
Plus there is the age of each candidate and the time of year the exam is taken.
What I mean to say is that the calculations seem to work more or less, but it is good to add a good margin +/- because there must be other things to consider, nothing strange, just statistics
Giulio

[waitingagain]

Hi Guilo/stressed parent
do you think 241 ooc for non such is a fairly safe bet before filling out CAF?
thoughts appreciated/

[stressedparent]

Hi waitingagain,

Definitely a yes you have nothing to lose with that score, your DD must be on the 91.5 percentile top 8.5%. A rank order of 118 +/- 4. Good luck to you and your DD on 1st March.


stressedparent