Refer to the American Journal of Science (Jan. 2005) study of the chemical makeup of buried glacial drifts (or tills) in Wisconsin, Exercise 7.64. The data on the ratios of aluminum (Al) to beryllium (Be) in sediment for a sample of 26 buried till specimens is reproduced in the table.
a. Use the bootstrap procedure to estimate the true proportion of till specimens with an Al/Be ratio that exceeds 4.5 using a 95% confidence interval.
b. Compare the bootstrap interval with the interval you obtained in Exercise 7.56, part b. Why might the bootstrap interval be more appropriate?

Data from Exercise 2.22

Tills are glacial drifts consisting of a mixture of clay, sand, gravel, and boulders. Engineers from the University of Washington’s Department of Earth and Space Sciences studied the chemical makeup of buried tills in order to estimate the age of the glacial drifts in Wisconsin. (American Journal of Science, Jan. 2005.) The ratio of the elements aluminum (Al) and beryllium (Be) in sediment is related to the duration of burial. The Al/Be ratios for a sample of 26 buried till specimens are given in the table. With the aid of a graph, estimate the proportion of till specimens with an Al/Be ratio that exceeds 4.5.

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TILLRATIO 3.76 4.05 3.81 3.23 3.13 3.30 3.21 3.32 4.09 3.90 5.06 3.85 3.88 4.06 4.56 3.60 3.27 4.09 3.38 3.37 2.73 2.95 2.25 2.73 2.55 3.06