The article cited in Exercise 34 in Section 7.3 gave the following summary data on proportional stress limits for specimens constructed using two different types of wood:

Type Sample Sample Sample of Wood Size Mean SD Red oak 14 8.48 .79 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 1 MPa.