How heavy a load (pounds) is needed to pull apart pieces of Douglas fir 4 inches long and 1.5 inches square? Here are data from students doing a laboratory exercise...
a) We are willing to regard the wood pieces prepared for the lab session as an SRS of all similar pieces of Douglas fir. Engineers also commonly assume that characteristics of materials vary Normally. Make a graph to show the shape of the distribution for these data. Does the Normality condition appear safe? Suppose that the strength of pieces of wood like these follows a Normal distribution with standard deviation 3000 pounds.
b) Give a 90% confidence interval for the mean load required to pull wood apart.
The above exercise gives data on the pounds of load needed to pull apart pieces of Douglas fir. The data are a random sample from a Normal distribution with standard deviation 3000 pounds.
a) Is there significant evidence at the α = 0.10 level against the hypothesis that the mean is 32,000 pounds for the two-sided alternative?
b) Is there significant evidence at the α = 0.10 level against the hypothesis that the mean is 31,500 pounds for the two-sided alternative?
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