Example: Low Power

Success = Yes, I recycle.

Gender X N Sample p

Male 33 59 0.559322

Female 54 79 0.683544

Estimate for p(1) - p(2): -0.124222

95% CI for p(1) - p(2): (-0.287215, 0.0387704)

Test for p(1) - p(2) = 0 (vs not = 0): Z = -1.49

P-Value = 0.135

A number of students said that they were surprised that the hypothesis test said “no difference in percentages.”