(Round all intermediate calculations to at least 4 decimal places.) 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. 

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? (Negative values should be indicated by a minus sign. Round your answer to 2 decimal places.) 
Test statistic 
The pvalue is:  

c. 
At α = 0.05, do you reject the null hypothesis? 

Test using the critical value approach with α = 0.05. 
d1. 
Calculate the critical value. (Negative value should be indicated by a minus sign. Round your answer to 2 decimal places.) 
Critical value 
d2. 
What is the conclusion? 

The statistical software output for this problem is:
Hence,
a) H_{0}: p ≥ 0.82; H_{A}: p < 0.82
b) Test statistic = 2.58
pvalue < 0.01
c) Yes, since the pvalue is smaller than α.
d  1) Critical value = 1.65
d  2) The law has been effective since the value of the test statistic falls in the rejection region.
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