[EX09-057] The density of the earth relative to the density of water is known to be 5.517 g/cm3.

Henry Cavendish, an English chemist and physicist

(1731–1810), was the first scientist to accurately measure the density of the earth. Following are 29 measurements taken by Cavendish in 1798 using a torsion balance. 5.50 5.61 4.88 5.07 5.26 5.55 5.36 5.29 5.58 5.65 5.57 5.53  5.62 5.29  5.44 5.34  5.79 5.10  5.27 5.39 5.42 5.47 5.63 5.34 5.46 5.30 5.75 5.68 5.85 Source: The data and descriptive information are based on material from “Do robust estimators work with real data?” by Stephen M. Stigler, Annals of Statistics, 5 (1977), 1055–1098.

a. What evidence do you have that the assumption of normality is reasonable? Explain.

b. Is the mean of Cavendish’s data significantly less than today’s recognized standard? Use a 0.05 level of significance.