Determine (a) the x² test statistic, (b) the degrees of freedom, (c) the critical value using α = 0.05, and (d) test the hypothesis at the α = 0.05 level of significance.
Outcome Observed Expected
A 39 40
B 42 40
C 39 40
D 40 40
H₀: pA = pB = pC = pD = 1/4
H₁: At least one of the proportions is different from the others.