15.11 Cell phones and reaction times Example 13 in Chapter 10 compared reaction times in a simulated driving test for the same students when they were using a cell phone and when they were not. The table shows data for the first four students.

For all 32 students, 26 had faster reaction times when not using the cell phone and 6 had faster reaction times when using it.

a. Are the observations for the two treatments independent samples or dependent samples? Explain.

b. Let p denote the population proportion who would have a faster reaction time when not using a cell phone.

Estimate p based on this experiment.

c. Using all 32 observations, find the test statistic and the P-value for the sign test of H0: p = 1>2 against Ha: p 7 1>2. Interpret.

d. What is the parametric method for comparing the scores? What is an advantage of it over the sign test? (Hint: Does the sign test use the magnitude of the difference between the two scores or just its direction?)

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Reaction times in cell phone study Using Cell Phone? Student No Yes Difference 1234 1 604 636 32 556 623 67 540 615 75 4 522 672 150