Plutonium has been produced in Hanford, Washington, since the 1940s, and some radioactive waste has leaked into the Columbia River, possibly contaminating the water supplies of Oregon residents living near the river. A 1965 study [3]

of the statistical relationship between proximity to the Columbia River and cancer mortality compared an exposure index and the annual cancer mortality rate per 100,000 residents for nine Oregon counties near the Columbia River

(Table 8.2).

a. Which variable would be the dependent variable in a simple linear regression model?

b. Does the estimated slope have a two-sided P value less than 0.05?

c. State the null hypothesis in words, not symbols.

d. What is the value of R²?

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Exposure index 11.64 8.34 6.41 Cancer mortality 207.5 210.3 177.9 3.83 3.41 2.57 2.49 162.3 129.9 130.1 147.1 1.62 137.5 1.25 113.5