The average age of a combined group of mean and women is 25 yr. If the average age of the group of men is 26 yr. and that of the group of women is 21 yr, then the percentage of men and women in the group is respectively

Consider the following statements

1. If 10 is added to each entry on a lists, then the average increases by 10.

2. If 10 is added to each entry on a list, then the standard deviation increases by 10.

3. If each entry on a list is doubled then the average doubles.

Which of the above statements are correct?

The variance of 25 observations is 4. If 2 is added to each observation, then the new variance of the resulting observations is

If the regression coefficient of Y on X is $$-$$6 and the correlation coefficient between X and Y is $$ - {1 \over 2}$$, then the regression coefficient of X on Y would be