(a) Construct and interpret a 95% large-sample confidence interval for the difference in the proportion using a cell phone while driving before the ban and the proportion after the ban. (b)Is 0 included in the confidence interval of Part (a)? What does this imply about the difference in the population proportions?
The Insurance Institute for Highway Safety issued a news release titled “Teen
Drivers Often Ignoring Bans on Using Cell Phones” (June 9, 2008). The following quote
is from the news release:
Just 1–2 months prior to the ban’s Dec. 1, 2006, start, 11% of teen drivers
were observed using cell phones as they left school in the afternoon. About 5
months after the ban took effect, 12% of teen drivers were observed using cell
phones.
Suppose that the two samples of teen drivers (before the ban, after the ban) are repre-
sentative of these populations of teen drivers. Suppose also that 200 teen drivers were
observed before the ban and that 150 teen drivers were observed after the ban.
(a) Construct and interpret a 95% large-sample confidence interval for the
difference in the proportion using a cell phone while driving before the ban and the
proportion after the ban.
(b)Is 0 included in the confidence interval of Part (a)? What does this
imply about the difference in the population proportions?
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