It is currently Sat Dec 03, 2016 5:43 pm

 All times are UTC

 Page 1 of 1 [ 7 posts ]
 Print view Previous topic | Next topic
Author Message
 Post subject: Percentiles: how do you work them out?Posted: Mon Mar 18, 2013 12:10 pm

Joined: Tue Dec 23, 2008 4:22 pm
Posts: 526
Location: Tonbridge & Tunbridge Wells
Hi all

I often read people quoting their DC is in the 96th percentile for VR etc etc., and have often wondered how they are calculated?

Any help would be welcomed as we are trying to calculate these for an appeal.

Our DS's 11-plus raw scores / marks we need the percentiles for are as follows:

VR - 141 (raw score 64 out of 80 correct)
NVR - 141 (raw score 50 out of 72 correct)

Top

 Post subject: Re: Percentiles: how do you work them out?Posted: Mon Mar 18, 2013 12:41 pm

Joined: Mon Aug 22, 2011 8:20 pm
Posts: 1706
Location: Warwickshire
Have a look here for an explanation of standardised scores. A score of 141 for a typical educational attainment test is in the top 1%. It depends whether your test has been scored against a whole population (e.g. Bucks, Kent) or against the cohort who took the test (e.g. Birmingham, Warwickshire) though - as you can't compare results between the two. However the number scoring full marks for a test which is predictable and tutored for tends to exceed the number you would statistically expect (hence the current move in many places towards tests which are more "tutor proof").

Top

 Post subject: Re: Percentiles: how do you work them out?Posted: Mon Mar 18, 2013 12:55 pm

Joined: Tue Dec 23, 2008 4:22 pm
Posts: 526
Location: Tonbridge & Tunbridge Wells
Okanagan wrote:
Have a look here for an explanation of standardised scores. A score of 141 for a typical educational attainment test is in the top 1%. It depends whether your test has been scored against a whole population (e.g. Bucks, Kent) or against the cohort who took the test (e.g. Birmingham, Warwickshire) though - as you can't compare results between the two. However the number scoring full marks for a test which is predictable and tutored for tends to exceed the number you would statistically expect (hence the current move in many places towards tests which are more "tutor proof").

Many thanks Okanagan for your help

We are based in Kent. Would it be better for us to contact NFER to get an accurate percentile for our DS's scores above?

Kind regards

Top

 Post subject: Re: Percentiles: how do you work them out?Posted: Mon Mar 18, 2013 1:17 pm

Joined: Mon Aug 22, 2011 8:20 pm
Posts: 1706
Location: Warwickshire
In a normal distribution 141 is 99.68% if you want to be exact. But at the extreme ends of the scale the values aren't statistically accurate - hence the reason that scores above 141 aren't published. And higher scores are clearly possible since the scores you are quoting are nowhere near 100% on raw scores.

In Kent for 2012 entry 76 children scored 418, 98 scored 419, and 589 scored the maximum 420.
For 2013 entry (with an increased maximum of 423 - i.e. 3 x 141) 880 scored over 420 for 2013, including over 660 on the full 423.

Clearly that's a lot more than 1% scoring 141 on every section as there obviously weren't over 66000 children taking the Kent test!

Top

 Post subject: Re: Percentiles: how do you work them out?Posted: Mon Mar 18, 2013 1:59 pm

Joined: Mon Dec 12, 2005 5:26 pm
Posts: 7059
Kent is (to date) relatively straightforward, and I would have thought appeal panels would normally focus on just the standardised score - and have no problem accepting that 141 is at the 99th percentile.

Incidentally, appeal panels will usually be familiar with percentiles and national standardisation from the evidence of CATs which appellants sometimes put forward.
See the table in B28(d):
http://www.elevenplusexams.co.uk/appeal ... cation#b28

I'm not aware of any meaningful percentiles for the Bucks 11+, because LA representatives used to say it was standardised for the cohort. KenR, on the other hand, has described it as "a bespoke hybrid approach which results in a test mean (average) of about 111-112 rather than 100".

_________________
Etienne

Top

 Post subject: Re: Percentiles: how do you work them out?Posted: Mon Mar 18, 2013 2:19 pm

Joined: Tue Dec 23, 2008 4:22 pm
Posts: 526
Location: Tonbridge & Tunbridge Wells
Etienne wrote:
Kent is (to date) relatively straightforward, and I would have thought appeal panels would normally focus on just the standardised score - and have no problem accepting that 141 is at the 99th percentile.

Incidentally, appeal panels will usually be familiar with percentiles and national standardisation from the evidence of CATs which appellants sometimes put forward.
See the table in B28(d):
http://www.elevenplusexams.co.uk/appeal ... cation#b28

I'm not aware of any meaningful percentiles for the Bucks 11+, because LA representatives used to say it was standardised for the cohort. KenR, on the other hand, has described it as "a bespoke hybrid approach which results in a test mean (average) of about 111-112 rather than 100".

Many thanks

Would it be possible (or correct) to quote a percentile figure for a combined Kent score (VR, NVR & Maths)? If so in our case we have a combined score of 400 out of a maximum 423.

Many thanks

Top

 Post subject: Re: Percentiles: how do you work them out?Posted: Mon Mar 18, 2013 2:29 pm

Joined: Mon Aug 22, 2011 8:20 pm
Posts: 1706
Location: Warwickshire
You can't really aggregate standardised scores and then expect to just divide by 3 to get the equivalent of one, and then give a percentile, as there will be an element of "regression towards the mean" - but if you could 133/141 would be about 98.68%.

You might be able to ask Kent admissions if they could give a figure for what percentage of candidates (or even x out of y candidates) scored an aggregate of 400 or above.

Top

 Display posts from previous: All posts1 day7 days2 weeks1 month3 months6 months1 year Sort by AuthorPost timeSubject AscendingDescending
 Page 1 of 1 [ 7 posts ]

 All times are UTC

#### Who is online

Users browsing this forum: No registered users and 1 guest

 You cannot post new topics in this forumYou cannot reply to topics in this forumYou cannot edit your posts in this forumYou cannot delete your posts in this forumYou cannot post attachments in this forum

Search for:
 Jump to:  Select a forum ------------------ FORUM RULES    Forum Rules and FAQs 11 PLUS SUBJECTS    VERBAL REASONING    MATHS    ENGLISH    NON-VERBAL REASONING    CEM 11 Plus GENERAL    GENERAL 11 PLUS TOPICS    11 PLUS APPEALS    11 PLUS TUTORS    INDEPENDENT SCHOOLS    11 PLUS CDs/SOFTWARE    11 PLUS TIPS    PRIMARY    SEN and the 11 PLUS    EVERYTHING ELSE .... 11 PLUS REGIONS    Berkshire    Bexley and Bromley    Birmingham, Walsall, Wolverhampton and Wrekin    Buckinghamshire    Devon    Dorset    Essex    Essex - Redbridge    Gloucestershire    Hertfordshire (South West)    Hertfordshire (Other and North London)    Kent    Lancashire & Cumbria    Lincolnshire    Medway    Northern Ireland    Surrey (Sutton, Kingston and Wandsworth)    Trafford    Warwickshire    Wiltshire    Wirral    Yorkshire BEYOND 11 PLUS    Beyond 11 Plus - General    GCSEs    6th Form    University