A recent study by Allstate Insurance Co. finds that 82% of teenagers have used cell phones while driving (The Wall Street Journal, May 5, 2010). In October 2010, Massachusetts enacted a law that forbids cell phone use by drivers under the age of 18. A policy analyst would like to determine whether the law has decreased the proportion of drivers under the age of 18 who use a cell phone. Use Table 1 and Table 2.
a.
Select the null and the alternative hypotheses to test the policy analyst’s objective.
H0: p = 0.82; HA: p ? 0.82
H0: p ? 0.82; HA: p < 0.82
H0: p ? 0.82; HA: p > 0.82
b.
Suppose a sample of 200 drivers under the age of 18 results in 150 who still use a cell phone while driving. What is the value of the test statistic? What is the p-value? (Negative values should be indicated by a minus sign. Do not round intermediate calculations. Round “test statistic” to 2 decimal places and “p-value” to 4 decimal places.)
Test statistic
p-value
c.
At ? = 0.05 has the law been effective?
Yes
No
Test using the critical value approach with ? = 0.05.
d-1.
Calculate the critical value. (Negative value should be indicated by a minus sign. Round your answer to 2 decimal places.)
Critical value
d-2.
Interpret the results.
Reject H0
Do not reject H0
