The article “Characterization of Bearing Strength Factors in Pegged Timber Connections” (J. Struct. Engr. 1997: 326–332) gave the following summary data on proportional stress limits for specimens constructed using two different types of wood:

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.

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Type of wood Red oak Douglas fir Sample size 14 10 Sample mean 8.48 6.65 Sample SD .79 1.28