Help finding the covariance

Statistics
Tutor: None Selected Time limit: 1 Day

A nurse is interested in whether there is a relationship between daily levels of stress and likelihood of a heart attack. The stress scores (predictor variable) and risk of heart attack values (criterion variable) from a small sample of participants are depicted below

Stress Score- 5,2,0,1

Risk of Heart Attack- 1,8,2,5,

What is the covariance?

May 24th, 2015

The covariance is -1.5

This is actually a really bad example because there are so few data points (you would never use a sample size n=4). But, here is the formula:

1/(n-1)Sum(xi-xavg)(yi-yavg), where x=stress and y=risk of heart attack, and n=3 (4-1).

So the means are: 8/4=2; 16/4=4.

1/(3)[(5-2)(1-4)+(2-2)(8-4)+etc]


May 24th, 2015

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May 24th, 2015
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May 24th, 2015
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