One operation of a mill is to cut pieces of steel into parts that will later be used as the frame for front seats in an automotive plant. The steel is cut with a diamond saw, and the resulting parts must be within ± 0.005 inch of the length specified by the automobile company. The data come from a sample of 100 steel parts and are stored in Steel. The measurement reported is the difference, in inches, between the actual length of the steel part, as measured by a laser measurement device, and the specified length of the steel part. Determine whether the data appear to be approximately normally distributed by

a. Comparing data characteristics to theoretical properties.

b. Constructing a normal probability plot.