# Question

Following the March 24, 1989, grounding of the tanker Exxon Valdez in Alaska, approximately 35,500 tons of crude oil were released into Prince William Sound. The paper “The Deep Benthos of Prince William Sound, Alaska, 16 Months After the Exxon Valdez Oil Spill” (Feder and Blanchard, 1998) reports on an evaluation of deep benthic in fauna after the spill. Thirteen sites were selected for study. Seven of the sites were within the oil trajectory, and six were outside the oil trajectory. Collection of environmental and biological data at two depths, 40 m and 100 m, occurred in the period July 1– 23, 1990. One of the variables measured was population abundance (individuals per square meter). The values are given in the following table.

a. After combining the data from the two depths, does there appear to be a difference in population mean abundances between the sites within and outside the oil trajectory? Use α = .05.

b. Estimate the size of the difference in the mean population abundances at the two types of sites using a 95% confidence interval.

c. What are the required conditions for the techniques used in parts (a) and (b)?

d. Check to see whether the required conditions are satisfied.

a. After combining the data from the two depths, does there appear to be a difference in population mean abundances between the sites within and outside the oil trajectory? Use α = .05.

b. Estimate the size of the difference in the mean population abundances at the two types of sites using a 95% confidence interval.

c. What are the required conditions for the techniques used in parts (a) and (b)?

d. Check to see whether the required conditions are satisfied.

## Answer to relevant Questions

Refer to Exercise 6.46. Answer the following questions using the combined data for both depths. a. Use the Wilcoxon rank sum test to assess whether there is a difference in population abundances between the sites within and ...Refer to Exercise 6.50. a. Compare the mean drops in blood pressure for the low-dose group and the control group. Use α = .05 and report the level of significance. b. Estimate the size of the difference in the mean drops ...Based on the land office’s decision in the test of hypotheses, could it have made (select one of the following) a. A Type I error? b. A Type II error? c. Both a Type I and a Type II error? d. Neither a Type I nor a ...The following memorandum opinion on statistical significance was issued by the judge in a trial involving many scientific issues. The opinion has been stripped of some legal jargon and has been taken out of context. Still, ...Find the value that locates an area α in the upper tail of the F distribution; that is, find Fα for the following values of α and degrees of freedom. a. α = .05, df1 5 7, df2 = 9 b. α = .025, df1 = 9, df2 = 7 c. α = ...Post your question

0