I need help in this problem......please pay your kind attention to this ......thanks

1: Why we use correlation Analysis Technique?
2: A computer while computing the correlation coefficient between two variables x and y from 25 pairs of observations, obtained the following results:

It was, however discovered at the time of checking that he had copied down two pairs of observations as:

x y x y
10 9 instead of 15 7
8 6 11 8
Obtain the correct value of correlation coefficient between x and y.