As part of the multicar study, four fabrics are tested for flammability at the National Bureau of Standards. The following bum times in seconds are recorded after paper tab is ignited on the hem of a dress made of each fabric:
(a) State the statistical model and present the ANOVA table. With a= .05, test the null hypothesis of no difference in degree of flammability for the four fabrics.
If the null hypothesis is rejected, construct confidence interval to determine the fabric(s) with the lowest mean burn time. Plot the residuals and comment on the plausibility of the assumptions.
(b) If the tests had been conducted one at a time on a single mannequin, how would you have randomized the fabrics in this experiment?