A paper in the Journal of the Association of Asphalt Paving Technologists (Vol. 59, 1990) describes an experiment to determine the effect of air voids on percentage retained strength of asphalt. For purposes of the experiment, air voids are controlled at three levels; low (2€“4%), medium (4€“6%), and high (6€“8%). The data are shown in the following table.

(a) Do the different levels of air voids significantly affect mean retained strength? Use a = 0.01.
(b) Find the P-value for the F-statistic in part (a).
(c) Analyze the residuals from this experiment.
(d) Find a 95% confidence interval on mean retained strength where there is a high level of air voids.
(e) Find a 95% confidence interval on the difference in mean retained strength at the low and high levels of air voids.

Transcribed Image Text:

Air Voids Retained Strength (%) 90 106 69 80 78 80 90 79 103 91 70 95 88 92 Low 94 62 83 83 87 85 69 Medium High 76 69 85