Question

How heavy a load (in 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:

33,190 31,860 32,590 26,520 33,280

32,320 33,020 32,030 30,460 32,700

23,040 30,930 32,720 33,650 32,340

24,050 30,170 31,300 28,730 31,920

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 it appear safe to assume that the Normality condition is satisfied? Suppose that the strength of pieces of wood like these follows a Normal distribution with standard deviation 3000 pounds.

b) Give a 95% confidence interval for the mean load required to pull the wood apart.

Answer 1

we can check normality by histogram if its shape is symmetric then it is symmetric ow not