A summary data on proportional stress limits for specimens constructed using two different types of wood are shown below:
Type of wood Sample size Sample mean Sample St. Dev.
Red oak 14 8.50 .80
Douglas fir 10 6.65 1.28
Assuming that both samples were selected from normal distributions, carry out a test of hypotheses to decide whether the true average proportional stress limit for red oak joints exceeds that for Douglas fir joints by more than one Mpa at a confidence level alpha =.05?