Does stress age you? As part of an investigation, Epel et al. (2004) measured telomere length in blood mononuclear cells of healthy premenopausal women, each of whom was the biological mother and caregiver of a chronically ill child. Telomeres are complexes of DNA and protein that cap chromosomal ends. They tend to shorten with cell divisions and with advancing age. A scatter plot of the data is shown below. Telomere length is measured as a ratio compared to a standard. Chronicity is the number of years since the child’s diagnosis. The data in the scatter plot can be summarized as follows:

a. Describe the pattern in the scatter plot briefly in words. Is there a relationship? Is it positive or negative? Is it linear or nonlinear? Is it weak or strong?

b. Calculate the linear correlation between telomere length and the chronicity of caregiving.

c. Calculate a 95% confidence interval for the population correlation.

d. Provide an interpretation for the interval in part (c). What does the interval represent?

e. What are your assumptions in part (c)? Does the scatter plot support these assumptions? Explain.

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Telomere length (ratio) 1.8 1.6 1.4 1.2- 1.0- ..... 2 6 8 Chronicity (years) 4 10 12