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# Suitable graph or calculation to show correlation Watch

1. Does anyone know the best graph/diagram to show trend and correlation between variables?? And also the best calculation (standard deviation, Quartiles or whatever else that's not too complicated and is in AQA GCSE sttistics) to show the same thing, which is correlation between two variables. (excluding scatter graphs and spearman's rank because i've done those already!)
Thanks in advance for any replies!!
2. (Original post by Lumos24520)
Does anyone know the best calculation to show the correlation between two variables?
Back from my days of doing Edexcel GCSE statistics, I used Pearson's correlation coefficient on top of the techniques you used. It's not terribly complicated, but it takes some work to use - best to confirm your calculations using an Excel spreadsheet.

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

That said you may want to look up books which cover a broad range of statistical techniques. A friend of mine did this to improve his coursework and got marginally better scores than me in GCSE statistics, but that's entirely down to you.

It should be noted that these things may not be in your syllabus, but if you are doing coursework much like I was then top marks are achieved by doing things which are related to, but not explicitly covered in, the syllabus.

I hope that helps.

Darren
3. (Original post by Lumos24520)
Does anyone know the best graph/diagram to show trend and correlation between variables?? And also the best calculation (standard deviation, Quartiles or whatever else that's not too complicated and is in AQA GCSE sttistics) to show the same thing, which is correlation between two variables. (excluding scatter graphs and spearman's rank because i've done those already!)
Thanks in advance for any replies!!
If you have a Casio 991ES you can go to Stat mode>a+bx mode type in the data for both the variables. Then press AC, shift stat and then regression and the r value. that will give you the product moment coerrelation coefficient.
The b value will give you the gradient.
4. (Original post by Lumos24520)
Does anyone know the best graph/diagram to show trend and correlation between variables?? And also the best calculation (standard deviation, Quartiles or whatever else that's not too complicated and is in AQA GCSE sttistics) to show the same thing, which is correlation between two variables. (excluding scatter graphs and spearman's rank because i've done those already!)
Thanks in advance for any replies!!
You could add a line of best fit to the scatter graph and work out the equation of the line. You would usually plot the mean of each variable as a point on the graph to help you with fitting the line (it should pass through this point). The equation can be used to interpolate values within the range of your data. You could use Microsoft Excel to add the line of best fit and determine the equation - Excel will produce a more accurate result than fitting by eye.

There are other correlation calculations you could do (e.g. PMCC) but they are outside what is expected at GCSE. Plotting histograms, cumulative frequency, box plots etc and working out mean, standard deviation, quartiles may be appropriate for your project they don't have anything to do with showing correlation.
5. (Original post by DPLSK)
Back from my days of doing Edexcel GCSE statistics, I used Pearson's correlation coefficient on top of the techniques you used. It's not terribly complicated, but it takes some work to use - best to confirm your calculations using an Excel spreadsheet.

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

That said you may want to look up books which cover a broad range of statistical techniques. A friend of mine did this to improve his coursework and got marginally better scores than me in GCSE statistics, but that's entirely down to you.

It should be noted that these things may not be in your syllabus, but if you are doing coursework much like I was then top marks are achieved by doing things which are related to, but not explicitly covered in, the syllabus.

I hope that helps.

Darren
Thanks so much for your advice!! It really did help!! I might do the syllabus thing, i'll look it up!
Again, thank you for your help it is much appreciated!!
6. (Original post by StUdEnTIGCSE)
If you have a Casio 991ES you can go to Stat mode>a+bx mode type in the data for both the variables. Then press AC, shift stat and then regression and the r value. that will give you the product moment coerrelation coefficient.
The b value will give you the gradient.
Thanks for trying but unfortunately i have a really old casio so i doubt that'll work :/
Thanks anyway!
7. (Original post by gdunne42)
You could add a line of best fit to the scatter graph and work out the equation of the line. You would usually plot the mean of each variable as a point on the graph to help you with fitting the line (it should pass through this point). The equation can be used to interpolate values within the range of your data. You could use Microsoft Excel to add the line of best fit and determine the equation - Excel will produce a more accurate result than fitting by eye.

There are other correlation calculations you could do (e.g. PMCC) but they are outside what is expected at GCSE. Plotting histograms, cumulative frequency, box plots etc and working out mean, standard deviation, quartiles may be appropriate for your project they don't have anything to do with showing correlation.
Oh my god!! Thank you so much!! i'd completely forgotten to do the line of best fit and that would definately lose me marks!! Yeah i'll definitely do that and I will take your advice on board and do the Excel thing that'll help a lot!!

And about the histogram, cumulative freqency, standard deviation and everything else, yes, they are mentioned in the guide but they don't show correlation which is what i'm most annoyed about!! I think the scatter diagrams and the spearman's rank showing the same thing will be enough to be honest because they kind of support each other in a way so I have proved my hypothesis already!!

Thanks for your advice it was VERY helpful!! I a bit more confident with my scatter graph now!!

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