5.38 ● The paper “Accelerated Telomere Shortening in Response to Life Stress” (Proceedings of the National Academy of Sciences [2004]: 17312–17315) described a study that examined whether stress accelerates aging at a cellular level. The accompanying data on a measure of perceived stress (x) and telomere length (y)

were read from a scatterplot that appeared in the paper. Telomere length is a measure of cell longevity.

Perceived Stress Telomere Length 5 1.25 6 1.32 6 1.5 7 1.35 10 1.3 11 1 12 1.18 13 1.1 14 1.08 14 1.3 15 0.92 15 1.22 15 1.24 17 1.12 17 1.32 17 1.4 18 1.12 18 1.46 19 0.84 Perceived Stress Telomere Length 20 1.22 20 1.30 20 1.32 21 1.24 21 1.26 21 1.30 22 1.18 22 1.22 22 1.24 23 1.18 24 1.12 24 1.50 25 0.94 26 0.84 27 1.02 27 1.12 28 1.22 29 1.30 33 0.94

a. Compute the equation of the least-squares line.

b. What is the value of r2?

c. Does the linear relationship between perceived stress and telomere length account for a large or small proportion of the variability in telomere length? Justify your answer.