An article in Polymer Degradation and Stability (2006, Vol. 91) presented data from a nine-year aging study on S537 foam. Foam samples were compressed to 50% of their original thickness and stored at different temperatures for nine years. At the start of the experiment as well as during each year, sample thickness was measured, and the thicknesses of the eight samples at each storage condition were recorded. The data for two storage conditions follow.

(a) Is there evidence to support the claim that mean compression increases with the temperature at the storage condition?

(b) Find a 95% confidence interval for the difference in the mean compression for the two temperatures.

(c) Is the value zero contained in the 95% confidence interval? Explain the connection with the conclusion you reached in part (a).

(d) Do normal probability plots of compression indicate any violations of the assumptions for the tests and confidence interval that you performed?

50C 0.047, 0.060, 0.061, 0.064, 0.080, 0.090, 0.118, 0.165, 0.183 60C 0.062, 0.105, 0.118, 0.137, 0.153, 0.197, 0.210, 0.250, 0.375