We are interested in determining whether there is a correlation between X and Y (either positive or negative) in the population from which we sampled. The data (from 8 subjects) are given below:

X	Y
1	2
2	7
5	3
7	9
6	4
11	10
12	6
15	18

Estimate the 'standard error of r' (i.e. the standard deviation of the possible values of r).

est. _r=?