How heavy a load (pounds) is needed to pull apart pieces   of Douglas fir 4in long and 1.5 inches square?  Here are the data   from students doing a laboratory exercise:         33,190         31,300     32,320         26,520     23,040         30,460     24,050         33,650     31,860         28,730     33,020         33,280     30,930         32,700     30,170         32,340     32,590         31,920     32,030      32,720           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 the wood apart.