# A-level maths (AQA) STATS

Discussion in 'Mathematics' started by -Maths-0000, Mar 12, 2019.

1. ### -Maths-0000New commenter

Hi. I am a pretty confused right now, regarding the topic of Correlation Coefficients. My [Hodder maths textbook](https://media.discordapp.net/attach...cs-Year-2-textbook-E.png?width=291&height=375) explains how to find Spearman's rank correlation coefficient, and a product moment correlation coefficient (PMCC), also providing questions to find them. However I looked in my [CGP revision guide](https://encrypted-tbn3.gstatic.com/...ZnoyNosyLzhl5crTwgYoM0ud_WtQ_e_cAVH0&usqp=CAE) (both are for the new 2017 spec) says [this](https://scontent.fbhx2-1.fna.fbcdn....=4e7a1bbc59d17f8d5f1e90cf16a15b4d&oe=5D286830), 'you only need to interpret the values of r (not find it)' where r is the PMCC. So I looked in the [official AQA teaching guidance document](https://allaboutmaths.aqa.org.uk/attachments/9406.pdf) and it says [this](https://scontent.fbhx2-1.fna.fbcdn....=c6e15d955ab99c00c57bf7e5b2ada16d&oe=5D1332F7), 'students will NOT be required to calculate a correlation coefficient'. So, from that I would just think that I won't bother learning this, and the formulae for it is also not in the AQA formula booklet. But today in maths at school we were taught how to find Spearman's rank correlation coefficient. I am so confused, please, if anyone knows, do we need to know these topics for AQA, or not? Thanks.

2. ### cach9801New commenter

It used to be on the A-Level - at least with Edexcel PMCC was S1, and Spearman's Rank was S3. I think it's good to learn where these come from to get an idea of what correlation actually means; however, I'm pretty sure calculating these will not be examined.

3. ### DustinFoxNew commenter

All the questions in the Oxford AQA text book seem to give the necessary PMCCs and simply ask for interpretation

4. ### MrMediaStar commenter

I think you are confusing assessment with curriculum. The assessment is a snapshot of some of the curriculum. You learn more than that which is assessed. A teacher is building on knowledge and understanding previously taught and preparing you for future pathways. Any teacher that teaches solely to the test isn’t doing you a good job. Once it has all been taught, then you look at the papers and ensure you can express some of your knowledge in a performance situation e.g. the exam.

Imagine showing up for uni and everyone else knew how to calculate a correlation coefficient and you didn’t. And then lots of other bits. You would say, how come my teacher didn’t teach me this and you all know? The same applies when you go to jobs and do recruitment tasks. They are looking for much wider knowledge than that in the exam.

PMCC: you do not need to know how to calculate it *in Year 1*.
You DO need to know in Year 2, see my instructions below.
You need to be able to interpret a value (eg "strong positive" and put this in context)
You need to be able to test if a value is significant against h0: rho=0 using a table of values given in the formula booklet

Regression line: you do not need to know how to calculate it (even though your Classwiz can)
You need to be able to interpret the gradient (eg "For every 1 hPa the air pressure goes up, the rainfall decreases by 0.223 mm")

Spearman's Rank: this is not in the A Level Maths syllabus

The specifications and specimen papers are all clear on this, as are the teaching guides
You can check for all exam boards in https://bit.ly/alevelmaths2017

I think MrMedia is confusing your question with an opportunity to preach a sermon.

No formula is required, as your new calculator does ALL the work for you
If you look on your Classwiz calculator you will see that you can enter data in Menu 6, choosing option 2: y=a+bx
It will then work out a, b and r for you
Watch this video by Calculator Guide

6. ### MrMediaStar commenter

Amen.

Every student that says...is it in the exam.

7. ### DamianRNew commenter

The subject content for A level Maths defined by Ofqual includes:

calculations involving regression lines are excluded

be able to interpret a given correlation coefficient using a given p-value or critical value (calculation of correlation coefficients is excluded)
This is carried straight across to the AQA spec. In particular for the hypothesis tests for correlation, the statement makes it clear that both the correlation coefficient and p-value or critical value will be given.

8. ### DamianRNew commenter

But it's curious that Edexcel carries those Ofqual statements into its specification, as required, so the content column states "calculation of correlation coefficients is excluded", yet the guidance column immediately to the right says "Students will be expected to calculate a value of r using their calculator but use of the formula is not required."

It seems that AQA have strictly interpreted the "given p-value or critical value" statement to mean that it will be given directly in a question, whereas Edexcel consider the provision of a table of values to meet the condition of a "given value".