Table A-6 lists critical values of r for selected values of n and a. More generally, critical r values can be found by using the formula 

where the t value is found from the table of critical t values (Table A-3) assuming a twotailed case with n - 2 degrees of freedom. Use the formula for r given here and in Table A-3 (with n - 2 degrees of freedom) to find the critical r values corresponding to H1: r ≠ 0, a = 0.02, and n = 27.