AP Statistics Tests of Significance

In 1975, a random sample of 1484 adult U.S. citizens was surveyed, and 193 strongly agreed with the statement, "People should take care of themselves". Then, in 1991, a survey of 1013 adult U.S. citizens showed that only 61 strongly agreed with the statement. Does this indicate that the proportion of U.S.adults who strongly agree with the given statement has dropped?

• Two-Sample Z Test for the Difference in Proportions

• Two-Sample T Test for the Difference in Means

• Matched Pairs T Test for a Mean

• One-Sample T Test for a Mean

A random sample of 49 medical doctors in LA showed that they worked an average of 53.1 hours/week with a standard deviation of 7.2 hours/week. If the California average is 60 hours/week, does this give evidence that the LA doctors work significantly less than the rest of California?

• One-Sample T Test for a Mean

• One-Sample Z Test for a Mean

• One-Sample T Test for a Proportion 

• One-Sample Z Test for a Proportion

White blood cell counts are normally distributed with mean 7500 and variance 500. If a patient has taken 50 laboratory blood tests that have a mean of 6899.75 and a standard deviation of 393.44, does this give evidence that his white blood cell count is significantly different than normal?

• One-Sample T Test for a Mean

• One-Sample Z Test for a Proportion

• One-Sample Z Test for a Mean

• One-Sample T Test for a Proportion

USA Today reported that in 1992, 39% of all elementary school children claimed that when they grow up they want to do something to help other people. However, in 1995, 128 of a random sample of 317 of these same children claimed that when they grow up they want to do something to help other people. Does this information indicate that there has been an attitude change either way?

• One-Sample Z Test for a Proportion

• Two-Sample Z Test for the Difference in Proportions

• One-Sample T Test for a Mean

• Two-Sample T Test for the Difference in Means

The following is based on information taken from Winter Wind Studies in Rocky Mountain National Park, by Glidden. At five weather stations on Trail Ridge Road in Rocky Mountain National Park, the peak wind gusts (mi/hr) in January and April are recorded below:
Weather station 1 2 3 4 5
January 139 122 126 64 78
April 104 113 100 88 61
Difference 35 9 26 -24 17
Does this information indicate that the peak wind gusts are higher in January than April?

• Two-Sample T Test for the Difference in

• Matched-Pairs T Test for a Mean

• One-Sample T Test for a Mean

• More females use social networking sites.
• In general, females use the sites more often than males.
• Approximately the same number of males and females were surveyed.
• About 43% of all students surveyed said they used social networking sites on a weekly basis.

• The slope decreased and the r² increased.
• The slope increased and the r² decreased.
• The slope decreased but r² remained the same.
• Both slope and r² remained the same.

What happens to the shape of the t-distribution as the degrees of freedom increase?

• The middle of the distribution becomes shorter, while the tails get higher, approximating a more uniform model.

• The distribution becomes more and more similar to a normal distribution.

• Nothing. But the results of the hypothesis test become less accurate.

• The middle of the distribution becomes shorter, while the tails get taller, resulting in a bimodal model.

What happens to the shape of the chi-square distribution as the degrees of freedom increase?

• Nothing.

• Eventually it will go from being right-skewed to normal.

• Eventually it will go from being right-skewed to left-skewed.

• It's peak will increase, becoming more right-skewed.

A random sample of 100 people from Country S had 15 people with blue eyes. A separate random sample of 100 people from Country B had 25 people with blue eyes. Assuming all conditions are met, which of the following is a 95 percent confidence interval to estimate the difference in population proportions of people with blue eyes (Country S minus Country B) ?

• (-0.01, 0.21)

• (-0.15,-0.05)

• (-0.19,-0.01)

• (-0.21, 0.01)

• (-0.24,0.04)