32 The minimum injection pressure psi for injection molding

32. The minimum injection pressure (psi) for injection molding specimens of high amylose corn was deter-mined for eight different specimens (higher pres-sure corresponds to greater processing dif culty), resulting in the following observations (from Ther-moplastic Starch Blends with a Polyethylene-Co-Vinyl Alcohol: Processability and Physical Proper-ties, Polymer Engrg. & Sci., 1994: 17—23):

15.0 13.0 18.0 14.5 12.0 11.0 8.9 8.0

a. Determine the values of the sample mean, sample median, and 12.5% trimmed mean, and compare these values.

b. By how much could the smallest sample obser-vation, currently 8.0, be increased without af-fecting the value of the sample median?

c. Suppose we want the values of the sample mean and median when the observations are expressed in kilograms per square inch (ksi) rather than psi. Is it necessary to reexpress each observation in ksi, or can the values calculated in part (a) be used directly? Hint: 1 kg 2.2 lb.

Solution