A study of two wind turbine models made by Vortex Milestone is being conducted to determine whether there is a difference in the peak efficiency rating for the two models. In the study, a sample of ten VX4 models and a sample of ten VX5 models are observed under similar operating conditions. The average peak efficiency rating for the ten VX4 models turns out to be 89.2 (on a scale of 0 to 100), with a sample standard deviation of 6.0. For the VX5 sample, the average peak efficiency rating is 87.2, with a standard deviation of 4.0. Set up hypothesis test to determine if the difference in sample mean ratings is statistically significant at the 5% significance level.