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...

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.