Refer to the NASA Polymer case in problems 7, 8, and 10.
(a) Find the five sample standard deviations (of percent weight loss) for the five different polymer resins
(b) Transform the data for the five polymer resins given in by taking the natural logarithm of each percent weight loss. Then find the five sample standard deviations for the logged values.
(c) Consider the two sets of standard deviations in (a) and (b). Which set is more consistent? What relevance does this comparison have to the use of the methods in Sect. 5.1?
(d) Find the five different sample means of log percent weight loss. Find the five sets of residuals for log percent weight loss (by subtracting sample log means from individual log values).
(e) Plot the residuals found in (d) versus the sample means from (d) (means of the log percent).
(f) Plot the residuals found in part (a) of versus the sample means (of percent weight loss). Compare the plot in (e) to this plot.
(g) Which set of data, the original one or the log transformed one, better satisfies the assumption of a common response variance for all five polymer resins?