# Spearmans Rank Correlation Coefficient in CourseworkWatch

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Thread starter 16 years ago
#1
I was told that using this method in my "Guesstimate" courseowrk would be useful. However I've forgotten what it would help me prove...HELP!!! I have the whole procedure done using values relating to how far off peoples results were from the actual size of what they were estimating I just need to know what each of the values will tell me exactly.
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16 years ago
#2
correlation
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Thread starter 16 years ago
#3
What I mean is what could I use it as evidence to prove. If I have my various correlations what can I say they prove?
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16 years ago
#4
The value r or the correlation co-efficient will give you a value for how strongly the ranks of the two data sets x and y, you are looking at, correlate with each other.

Anything above 0.75 can be said to be strong positive, (age of car, loss in value) when 1 is perfect positive.

<= -0.75 strong negative (age of car vs Value)

-1 Perfect Positive.

Otherwise weak pos/neg coming closer to zero, until about +ve and -ve .25 when there is little to no correlation.

This is best illustrated using a scatter graph first, describing what it looks like, THEN using Spearman to put a quantity to your observations.
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Thread starter 16 years ago
#5
I used standard deviation in an earlier part of my coursework. How easy is it to compare SD and SRCC?
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16 years ago
#6
(Original post by ChrisR)
I used standard deviation in an earlier part of my coursework. How easy is it to compare SD and SRCC?
The two aren't related in themselves, though you could talk a little about the fact that a wide standard deviation will show more spread from the mean values on a scatter graph.

Don't go down this road without knowing what you are talking about though.
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16 years ago
#7
The spearman value is used when a graph is not roughly linear or elliptical (as opposed to PMCC when it is roughly linear or elliptical.) It can be used to show if there is or isn't correlation between two sets of values, eg: age of a car and price. You need to rank the data in order and the calcualte you rs value.

eg: Age Price Rank x Rank y d*2
2 5000 1 2 1
5 4050 3 1 4
3 6000 2 3 1

D*2 is the difference between rank x and rank y squared.

Rs= 1- 6 x sumd*2
n(n*2-1)

Calculate the Rs value ,as in here, 1-6x6
3x(3*2-1) = 0.5

Use table to find critical value. (n=3 and significance level eg: 5%)

State Ho and H1 and show that the test stat (here 0.5) is either greater than the c.v. or less than. This will show that you should accept H0 or H1, which ever is this case and then you can talk about this shows hows there is rank correltion or isn't what ever you stated in your hypothesis'.

Hope this helps, I know how to do it, it just isn't easier to explain over thenet, (without a diagram etc.)
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16 years ago
#8
Quick tip- don't put spearmans... in your coursework unless you have to. Examiners will mark you down for using techniques you don't have to.
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Thread starter 16 years ago
#9
Has anyone got a copy of a significance table or do you have to calculate this yourself?
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16 years ago
#10
I have it somewhere in my GCSE statistics textbook but I only read it yesterday...

EDIT: I mean how to calculate the thingy not a table
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16 years ago
#11
(Original post by ChrisR)
Has anyone got a copy of a significance table or do you have to calculate this yourself?
I found an online copy of the significance tables. You'll need Acrobat to read it though.

Hope that's of some help!
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15 years ago
#12
hi ive started my coursework.
Im doing the colour test.
i am doing y7 girls word y7 girls colour
y10 boy and girl word and colour and so on
Im not sure which ones to do the spearmans rank on.
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15 years ago
#13
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15 years ago
#14
what does it mean by a two tailed test in that pdf document ?

Would river width by depth in spearmans rank be a 2 or 1 tailed test ???
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