Does heavy cell phone use affect brain activity? There is some concern about possible negative effects of radiofrequency signals delivered to the brain. In a randomized matched-pairs study, 47 healthy participants had cell phones placed on the left and right ears. Brain glucose metabolism (a measure of brain activity) was measured for all participants under two conditions: with one cell phone turned on for 50 minutes (the ‘‘on” condition) and with both cell phones off (the ‘‘off” condition). The amplitude of radio frequency waves emitted by the cell phones during the ‘‘on” condition was also measured.

(a) Is this an experiment or an observational study? Explain what it means to say that this was a ‘‘matched-pairs” study.

(b) How was randomization likely used in the study? Why did participants have cell phones on their ears during the ‘‘off” condition?

(c) The investigators were interested in seeing whether average brain glucose metabolism was different based on whether the cell phones were turned on or off. State the null and alternative hypotheses for this test.

(d) The p-value for the test in part (c) is 0.004. State the conclusion of this test in context.

(e) The investigators were also interested in seeing if brain glucose metabolism was significantly correlated with the amplitude of the radiofrequency waves. What graph might we use to visualize this relationship?

(f) State the null and alternative hypotheses for the test in part (e).

(g) The article states that the p-value for the test in part (e) satisfies p < 0.001. State the conclusion of this test in context.