Which Quartile Definition for Leaving Cert??

ray giraffe

There are at least 3 different possibilities for the definitions of quartiles:

http://en.wikipedia.org/wiki/Quartile

Which definition is used for Leaving Cert Maths? :eek:

Leaving Cert Student

ray giraffe wrote: »

There are at least 3 different possibilities for the definitions of quartiles:

http://en.wikipedia.org/wiki/Quartile

Which definition is used for Leaving Cert Maths? :eek:

it is the 25th percentile?

locum-motion

ray giraffe wrote: »

There are at least 3 different possibilities for the definitions of quartiles:

http://en.wikipedia.org/wiki/Quartile

Which definition is used for Leaving Cert Maths? :eek:

That article defines the 1st, 2nd and 3rd quartiles.

It does not provide three different definitions for 'quartile'.

MathsManiac

locum-motion wrote: »

That article defines the 1st, 2nd and 3rd quartiles.

It does not provide three different definitions for 'quartile'.

If you scroll down a bit, you'll see that it gives three different methods of calculation, which are, in effect, three different definitions, (since in general they give different results).

In my view, percentiles (including quartiles) are really only useful and meaningful when the data sets are large, in which case all of the definitions will effectively give the same result.

For small data sets, I assume that different teachers might use different methods, and that all of them would be acceptable.

locum-motion

The OP said "there are three possibilities for definitions" on the page.
Since the OP was specifically talking about 'definitions', that is the part of the Wikipedia page that I looked at.
The 'Definitions' section does not say what the OP said it says.
It does say what I said it says.
So I stand over my post.

MathsManiac wrote: »

If you scroll down a bit, you'll see that it gives three different methods of calculation, which are, in effect, three different definitions, (since in general they give different results).

In my view, percentiles (including quartiles) are really only useful and meaningful when the data sets are large, in which case all of the definitions will effectively give the same result.

For small data sets, I assume that different teachers might use different methods, and that all of them would be acceptable.

ray giraffe

Leaving Cert Student wrote: »

it is the 25th percentile?

Yes, but then we have to decide on the definition of percentile!

MathsManiac wrote: »

For small data sets, I assume that different teachers might use different methods, and that all of them would be acceptable.

That's what I hope. Marking schemes should have at least 3 possible answers!

locum-motion wrote: »

The OP said "there are three possibilities for definitions" on the page.
Since the OP was specifically talking about 'definitions', that is the part of the Wikipedia page that I looked at.
The 'Definitions' section does not say what the OP said it says.
It does say what I said it says.
So I stand over my post.

Thank you for your very helpful reply.