Question: (From 1997 final exam). Recent studies have suggested that a significant negative correlation exists between subjects' cerebral glucose metabolic rate (CGMR) and their scores on a standardized test of intelligence (IQ). That is, subjects who metabolize less glucose obtain higher IQ test scores. In an attempt to replicate this negative correlation, a researcher measures the CGMR of 8 young adult subjects as they work on an IQ test. The following data were obtained, where CGMRs are expressed as Z scores:

Subjects CGMR IQ

1 .70 114
2 1.50 101
3 -1.01 133
4 -.14 128
5 .13 111
6 .85 92
7 -1.47 122
8 -.56 107

a) Has this study successfully replicated the significant negative correlation between CGMR and IQ (α = .05)?

b) Regardless of your answer in part 'a', use the given sample data to generate a 99% prediction interval for the IQ score of a subject with a CGMR Z score of +.44.

c) Among older adults, the slope for predicting IQ scores from CGMR is -12.4. Is the slope in the present sample of young adults significantly different from this (α = .05)?