Investigation 7: “White coat effect” (due Tues, Feb 7)

You may work with one other person on this assignment, handing in one report with both names.  Word-processed reports are preferred to hand-written ones.  Please copy/paste relevant, well-labeled Minitab output into a Word file as appropriate.

It has been conjectured that talking about one’s medical history might create stress that elevates a person’s blood pressure. If this is true, then a person’s blood pressure might tend to be higher when measured in a doctor’s office (hence the term “white coat effect”) than in a less stressful environment. To investigate this conjecture, researchers conducted a study in which 16 patients with high blood pressure were randomly assigned to one of two groups before their blood pressure was measured: one group (“talking”) was asked questions about their medical history while the other group (“counting”) was asked to count aloud from 1 to 100. The diastolic blood pressure measurements (in millimeters of Hg) for these 16 patients were:

Talking group: 104, 110, 107, 112, 108, 103, 108, 118

Counting group: 110, 96, 103, 98, 100, 109, 97, 105

a) Is this an observational study or a controlled experiment? Explain.

b) Identify the explanatory variable and the response variable.

c) State in words and symbols the hypotheses for testing whether these data provide evidence of a “white coat effect.”

d) Conduct the appropriate t-test. Report the value of the test statistic and also the P-value. (Feel free to use Minitab to do the calculations, but you will have to enter the data yourself.) Also indicate what test decision you would make at the alpha = .05 significance level, and summarize your conclusion in context.

e) Produce and interpret a 95% confidence interval for the difference in population mean blood pressures.

f) Investigate and comment on whether the technical conditions required for the validity of this t-test and t-interval are satisfied.

g) Does the design of this study allow you to draw a cause/effect conclusion? Explain why or why not.