Nonsuch/Wallington Girls Test results 2017

[sriji]

It's so surprising to have no information on closing scores for wallington girls. I wished school had published last year closing/intake data as it seems they used to do in past. I tumbled on a old link (2013 result - http://www.wallingtongirls.sutton.sch.u ... ions-faqs)

[stateschoolman]

Use the following excel formula to estimate DD position amongst the cohort of 965 girls taking the Stage 2 Nonsuch & Wallington Girls Tests :-

=965*(1-NORMDIST(SCORE,300,46,1))

Make sure to replace SCORE with your DD score !

For the math geeks :-
Note 1: Assuming normal distribution of scores and a mean/median of 300.
Note 2: you can test the formula with the lowest passing score (246) - which should be position 849
Note 3: The highest score (402) is an outlier unlike the lowest passing score (246) which has 116 scores below it - hence STD deviation of 46 calculated based on the lowest score(246) and the number of children NOT passing (116)

[hbsseal]

This is not correct.

a. 402 is not an outlier. It is not a raw score, it is a standardised score, so there are no outliers.
b. Rank 849 in terms of overall score is not someone with a score of 246, because there are others with higher scores but who did not make it.

Mean 300 and Std deviation 34 is the correct normal distribution.

[stateschoolman]

This is not correct.

a. 402 is not an outlier. It is not a raw score, it is a standardised score, so there are no outliers.
b. Rank 849 in terms of overall score is not someone with a score of 246, because there are others with higher scores but who did not make it.

Mean 300 and Std deviation 34 is the correct normal distribution.

We only have a few facts to estimate std deviation.

a. The highest standardised score is an outlier for reverse calculating std deviation.
b. agreed - my mistake. However, I believe the std deviation to be somewhere closer to 46 (pessimistic) than 34(optimistic).

FORMULA 1:
=965*(1-NORMDIST(SCORE,300,46,1))

FORMULA 2:
=965*(1-NORMDIST(SCORE,300,34,1))

[Gringo64]

This is not correct.

a. 402 is not an outlier. It is not a raw score, it is a standardised score, so there are no outliers.
b. Rank 849 in terms of overall score is not someone with a score of 246, because there are others with higher scores but who did not make it.

Mean 300 and Std deviation 34 is the correct normal distribution.

a. You can have outliers with standardised scores. Sometimes outliers are removed before standardising results, but that would not have been the case here.

[Letree]

if assuming there are 20 pupils (of course it just a simple guess) who score higher than 246 but fail because of individual subjects,
then the score 246 would be the 869th in the ranking in terms of score,

standard deviation would be 42.

This is not correct.

a. 402 is not an outlier. It is not a raw score, it is a standardised score, so there are no outliers.
b. Rank 849 in terms of overall score is not someone with a score of 246, because there are others with higher scores but who did not make it.

Mean 300 and Std deviation 34 is the correct normal distribution.

We only have a few facts to estimate std deviation.

a. The highest standardised score is an outlier for reverse calculating std deviation.
b. agreed - my mistake. However, I believe the std deviation to be somewhere closer to 46 (pessimistic) than 34(optimistic).

FORMULA 1:
=965*(1-NORMDIST(SCORE,300,46,1))

FORMULA 2:
=965*(1-NORMDIST(SCORE,300,34,1))

[Bluearrow]

Use the following excel formula to estimate DD position amongst the cohort of 965 girls taking the Stage 2 Nonsuch & Wallington Girls Tests :-

=965*(1-NORMDIST(SCORE,300,46,1))

Make sure to replace SCORE with your DD score !

For the math geeks :-
Note 1: Assuming normal distribution of scores and a mean/median of 300.
Note 2: you can test the formula with the lowest passing score (246) - which should be position 849
Note 3: The highest score (402) is an outlier unlike the lowest passing score (246) which has 116 scores below it - hence STD deviation of 46 calculated based on the lowest score(246) and the number of children NOT passing (116)

The standard deviation for exam results is normally set at 15. As the mean is 300, the equivalent of three single tests. So the standard deviation is normally 45, which is not far from your original guess of 46.

[hbsseal]

Thank you for all the comments above.

But SDs of normal distributions do not add up. Even if the individual scores were completely independent (which is definitely not the case here), it is variances that add up, not SD. In this case, the SD of overall score is around 34.

[stateschoolman]

Thank you for all the comments above.

But SDs of normal distributions do not add up. Even if the individual scores were completely independent (which is definitely not the case here), it is variances that add up, not SD. In this case, the SD of overall score is around 34.

Thank you also for getting the debate going.

With very little facts, these formulas are indeed "estimates" and just time fillers whilst we wait for the real results next year.

In the meanwhile, I'm sure there is another exam in waiting...

All the best !

[dsme]

Hello All , My DD got 309.6 in the test . We live in WD18... (Watford) , Should we put Nonsuch on CAF ? as DD liked the school but I am not sure if there is a chance . Help please ...

Thank you