A. A two-proportion z -test
B. A two-sample t -test
C. A matched pairs t -test
D. A chi-square test of independence
E. A chi-square goodness of fit test
Smartphones with larger screens tend to be more expensive than smartphones with smaller
screens. A random sample of currently available smartphones was selected. A 95% confidence
interval for the slope of the regression line to predict price from screen size is (61, 542). Which of
the following statements concerning this interval is correct?
A. If many samples of this size were taken, about 95% of confidence intervals for the slope based
on those samples would contain the slope of the line for all smartphones that are currently
available.
B. If many samples of this size were taken, about 95% of those samples would have a regression
line with a slope between 61 and 542.
C. There is convincing evidence that the size of the screen is the reason for the difference in price.
D. Because this interval is so large, there is not convincing evidence of a relationship between
screen size and price.
E. There is not enough information to make a statement about the relationship between screen size
and price because memory capacity and other features must also be taken into account.
- In the 50 states of the United States, the financial climate for people living in retirement varies.
Some states are very tax friendly to retirees. Other states are much less tax friendly to retirees. As a
member of the Oregon state legislature, you wonder if Oregon’s tax policies are driving older,
retired people to move to other states. You have a cousin in Florida with the opposite idea—that the
tax-friendly nature of Florida attracts more retirees. Each of you takes a random sample of the
adults in your respective states and finds the statistics in the table below.
The 99% confidence interval for the difference in the mean age of adults in Oregon and adults in
Florida is (–16.73, 8.69). Does this interval provide convincing evidence that the mean ages of
adults in the two states differ?
A. Yes, because 0 is in the interval.
B. No, because 0 is in the interval.
C. Yes, because the mean ages are different in the two samples.
D. No, because the mean ages of the samples are less than one standard deviation apart.
E. Yes, because this is a t -interval for a difference in means.