Index of Biotic Integrity. The Ohio Environmental Protection Agency used the Index of Biotic Integrity (IBI)

to measure the biological condition, or “health,” of an aquatic region. The IBI is the sum of metrics that measure the presence, abundance, and health of fish in the region.

(Higher values of the IBI correspond to healthier fish populations.) Researchers collected IBI measurements for sites located in different Ohio river basins (Journal of Agricultural, Biological, and Environmental Sciences, June 2005). Summary data for two river basins, Muskingum and Hocking, are given in the accompanying table.

a. Use a 90% confidence interval to compare the mean IBI values of the two river basins. Interpret the interval.

b. Conduct a test of hypothesis (at a = .102 to compare the mean IBI values of the two river basins. Explain why the result will agree with the inference you derived from the 90% confidence interval in part a.

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Standard River Basin Sample Size Mean Deviation Muskingum Hocking 53 .035 1.046 51 .340 .960