# Normal Probability

Question

The spatial orientation skills of 30 male and 30 female students were challenged in a wooded park near the Boston College campus in Newton, Massachusetts. The participants were asked to rate their own sense of direction as either good or poor. In the park, students were instructed to point to predesignated landmarks and also to the direction of south. For the female students who had rated their sense of direction to be good, the table on page 341, provides the pointing errors (in degrees) when they   attempted to point south.

a. If, on average, women who   consider themselves to have a good sense of direction do no better than they   would by just randomly guessing at the direction of south, what would their   mean pointing error be?   b. At the 1% significance level, do the data provide sufficient evidence to conclude that women who consider themselves to have a good sense of direction really do better, on average, than they would by just randomly guessing at the direction of south? Use a one-mean t-test.

c. Obtain a normal probability plot, boxplot, and stem- and-leaf diagram of the data. Based on these plots, is use of the t-test reasonable? Explain your answer.

d. Use the technology of your   choice to perform the data analyses in parts (b) and (c).   Female Student Point Error (in   °)   1 14   2 122   3 128   4 109   5 12   6 91   7 8   8 78   9 31   10 36   11 27   12 68   13 20   14 69   15 18

Question

4. Exercise 10.78 (p.  438) Alcohol and Reaction Times   (Do the   problem by hand. Use the p-value approach). To test the effect of alcohol in   increasing the reaction time to respond to a given stimulus, the reaction   times of seven people were measured. After consuming 3 ounces of 40% alcohol,   the reaction time for each of the seven people was measured again. Do the   following data indicate that the mean reaction time after consuming alcohol   was greater than the mean reaction time before consuming alcohol? Use α=.05   Person 1 2 3   4 5 6 7   Before 4 5 5   4 3 6 2   After 7 8 3   5 4 5 5

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