Correlation?

Question

If you were given a chart that was in the form:
x: 1| 2| 3| 4| 5| 6| 7|
y: 4.1|4.2|4.4|4.6|4.7|5.0|5.2

what would be the correlation?
the options are -0.9, -0.3, 0.3 and 0.9.
How would you figure this out?
THANKS

Answer 1

Since you have multiple choice options, there is a shortcut to the formula for the correlation coefficient.

First, does it look like the values of y are increasing as the values of x increase? The answer is yes, so the correlation must be positive. If they were decreasing, the correlation would be negative.

Next, does it look like increasing x by a specific amount (like 1) usually gives the same amount of increase in y (like 0.1 or 0.2)? The answer is yes, so there must be a strong correlation. Strong correlations are close to 1 or -1.

We established that the correlation was strong and positive, so it would be highly likely that the correlation coefficient was 0.9.

Answer 2

I don't know if this will help. but you could take a look at

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