X = Viscosity of a polymer with Catalyst A was measured for 22 samples with resulted in sample average of 742 and standard deviation of 26. Independently, Y = viscosity of another polymer with Catalyst B was measured for 42 samples which resulted in sample average of 763 and standard deviation of 19. Suppose E(X_i) = (mu)_i and V(X_i) = (sigma)_i², i = 1, 2.
a) -t_22-1
b) -t_42-1
c) N(0, 1)
d) None of the above