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

The set of bivariate observations (x₁, y₁), (x₂, y₂), ....... (x_n, y_n) are such that all the values are distinct and all the observations fall on a straight line with non-zero slope. Then, the possible values of the correlation coefficient between x and y are

An analysis of monthly wages paid to the workers in two firms A and B belonging to the same industry gives the following result

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The average of monthly wage and variance of distribution of wages of all the workers in the firms A and B taken together are