Calculate a Pearson's r to determine the type and strength of the relationship

In a study on caffeine and stress, college students indicated how many cups of coffee they drink per day and their stress level on a scale of 1 to 10. The data are provided in the following table.

Number of Cups of Coffee Stress Level
3 5
2 3
4 3
6 9
5 4
1 2
7 10
3 5
2 3
4 8

Calculate a Pearson's r to determine the type and strength of the relationship between caffeine and stress level. How much of the variability in stress scores is accounted for by the number of cups of coffee consumed per day?

Hi,

check out wiki's page for "person product-moment correlation coefficient" for the formula, see where it says "Alternative formulae for the sample Pearson correlation coefficient are also available" that formula is probably the easiest to use. Its not hard its just time consuming. Do you know what the elements of the formula mean?

Hope that helps

Actually, I did check on Wikipedia and there wasn't anything mentioned about what the formula was for the pearson product-moment correlation coefficient. All it stated was giving an explanation about what the purpose of it was. I didn't see any formula of it. In response to your question, No I don't know what the elements of the formula mean. Can you explain to me what the elements of the formula mean? Can you help me with the above problem step-by-step? I have a learning disability so its hard for me to understand and grasp material. I am pretty stressed out because I have a Mid Term next week and am trying to understand this material and its over 6 chapters. Please help me if your able to.

rbcc said:

Hi,

check out wiki's page for "person product-moment correlation coefficient" for the formula, see where it says "Alternative formulae for the sample Pearson correlation coefficient are also available" that formula is probably the easiest to use. Its not hard its just time consuming. Do you know what the elements of the formula mean?

Hope that helps

Click to expand...

Hi

the formula is under mathematical properties I can't write it here I don't know how

http://en.wikipedia.org/wiki/Pearson_product-moment_correlation_coefficient


its where it says "Alternative formulae for the sample Pearson correlation coefficient are also available:"

so n means the number of data points you have
sigma x_iy_i means you have to multiply all the xs by the ys and add them up

sigma x means add up all the xs sigma y means the same for y

gigmax^2 means square all the x values and add them
sigma (x)^2 means add up all the xs then square the whole thing

the same for the ys
x y
3 5
2 3
4 3
6 9
5 4
1 2
7 10
3 5
2 3
4 8


n=10
sigma xy= (3*5)+(2*3)+(4*3)+(6*9)+... continue like that till you get to +(4+8)

sigma x = 3+2+4+6 contunie till you get to +4
sigma y is the same thing
sigma x^2= 3^1+2^2+4^2+6^2 continue
sigma (x)^2= your value for sigma x squared

then do the same for the ys sub those values in to the equation and solve

try watching this http://www.youtube.com/watch?v=2B_UW-RweSE&feature=related

Thanks for the information and I think that I have found the formula to use for the Pearson's r and doing the calculation. If I have any more questions about this then I will be more than happy to ask.

rbcc said:

Hi

the formula is under mathematical properties I can't write it here I don't know how

http://en.wikipedia.org/wiki/Pearson_product-moment_correlation_coefficient


its where it says "Alternative formulae for the sample Pearson correlation coefficient are also available:"

so n means the number of data points you have
sigma x_iy_i means you have to multiply all the xs by the ys and add them up

sigma x means add up all the xs sigma y means the same for y

gigmax^2 means square all the x values and add them
sigma (x)^2 means add up all the xs then square the whole thing

the same for the ys
x y
3 5
2 3
4 3
6 9
5 4
1 2
7 10
3 5
2 3
4 8


n=10
sigma xy= (3*5)+(2*3)+(4*3)+(6*9)+... continue like that till you get to +(4+8)

sigma x = 3+2+4+6 contunie till you get to +4
sigma y is the same thing
sigma x^2= 3^1+2^2+4^2+6^2 continue
sigma (x)^2= your value for sigma x squared

then do the same for the ys sub those values in to the equation and solve

try watching this http://www.youtube.com/watch?v=2B_UW-RweSE&feature=related

Click to expand...