A Summary Data on Proportional Stress Limits for Specimens Constructed

Essay

A summary data on proportional stress limits for specimens constructed using two different types of wood are shown below: $$\begin{array} { l c c c } \hline \text { Type of wood } & \text { Sample size } & \text { Sample mean } & \text { Sample St. Dev. } \\\hline \text { Red oak } & 14 & 8.50 & 80 \\\text { Douglas fir } & 10 & 6.65 & 1.28 \\\hline\end{array}$$ 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?