covariance of sets of scores is 0.73; find r between 2 sets

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pc678

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Math achievement scores of a group of students when they were 8 were correlated with the scores of the same group when they were 12. The scores were expressed as z-scores, the covariance is .73. What is the r between these 2 sets?

Kind of stumped on this question. Don't even know how to get started. Anyone have any tips? Do I look up .73 in my statistical tables or something?
 
Re: covariance/correlation problem

I don't know how i'm supposed to find the answer without the Standard Deviations, though.
 
Re: covariance/correlation problem

If you think about it. The mean of a zscore is always 0 and the sd is always 1

so .73/1=.73
 
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