13.19 The authors of the paper “Decreased Brain Volume in Adults with Childhood Lead Exposure” (Public Library of Science Medicine [May 27, 2008]: e112) studied the relationship between childhood environmental lead exposure and a measure of brain volume change in a particular region of the brain. Data were given for x 5 mean childhood blood lead level (mg/dL) and y 5 brain volume change (BVC, in percent). A subset of data read from a graph that appeared in the paper was used to produce the accompanying Minitab output.

Regression Analysis: BVC versus Mean Blood Lead Level The regression equation is BVC 5 20.00179 2 0.00210 Mean Blood Lead Level Predictor Coef SE Coef T P Constant 20.001790 0.008303 20.22 0.830 Mean Blood Lead Level 20.0021007 0.0005743 23.66 0.000 Carry out a hypothesis test to decide if there is convincing evidence of a useful linear relationship between x and y. Assume that the basic assumptions of the simple linear regression model are reasonably met.