Statistics Proportion and Mean

Scientists collect data on the blood cholesterol levels (milligrams per deciliter of blood) of a random sample of 25 laboratory rats. A 95% confidence interval for the mean blood cholesterol level μ is 80.2 to 89.8. Which of the following would cause the most worry about the validity of this interval?

• There is a clear outlier in the data

• A stemplot of the data shows a mild right skew

• You do not know the population standard deviation σ

• The population distribution is not exactly Normal.

• None of these are a problem when using t-interval

Many television viewers express doubts about the validity of certain commercials. In an attempt to answer their critics, Timex Group USA wishes to estimate the proportion of consumers who believe what is shown in Timex television commercials. Let p represent the true proportion of consumers who believe what is shown in Timex television commercials. What is the smallest number of consumers that Timex can survey to guarantee a margin of error of 0.05 or less at a 99% confident level?

• 550

• 600

• 650

• 700

• 750

What interval should be used?

• 2 Sample t interval for means

• Paired t interval

• Paired t test

• 1 proportion z interval

What test should be used?

• 2 proportion z test

• 1 proportion z test

• 2 sample t test for means

• 1 sample t test for mean

What interval should be used?

• 2 Proportion z interval

• 1 Proportion t interval

• 1 Proportion z interval

• Chi Square for Goodness of Fit

What test should be used?

• 2 Sample t test for difference in means

• 2 proportion z test

• Paired t test

• 1 sample z test

As part of a national sleep study, a random sample of adults was selected and surveyed about their physical activity and the number of hours they sleep each night. Of the 183 adults who exercised regularly (exercisers), 59 percent reported sleeping at least seven hours at night. Of the 88 adults who did not exercise regularly (nonexercisers), 52 percent reported sleeping at least seven hours at night. Which of the following is the most appropriate standard error for a confidence interval for the difference in proportions of adults who sleep at least seven hours at night among exercisers and nonexercisers?

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The management team of a company with 10,000 employees is considering installing charging stations for electric cars in the company parking lots. In a random sample of 500 employees, 15 reported owning an electric car. Which of the following is a 99 percent confidence interval for the proportion of all employees at the company who own an electric car?

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Mrs. Trahan claims that her students' average score on the AP exam is 3.9. A random sample of 50 of her students' scores produce a mean score of 3.1 with a standard deviation of 1.5. Does this sample show evidence that Mrs. Trahan is overstating her average score?

• With a test statistic of -3.8 which is unlikely, it seems that Mrs. Trahan may be overstating her average AP score.

• With a test statistic of -4.7 which is unlikely, it seems that Mrs. Trahan may be overstating her average AP score.

• With a test statistic of -0.53 which is not unusual and this sample does not show evidence that Mrs. Trahan is overstating her average AP score.

A random sample of 25 Ohio students had a mean ACT score of 21 with a standard deviation of 1.2.  Which of the following is the 95% confidence interval for the true average ACT score for Ohio students?

• (20.53, 21.47)

• (18.648, 23.352)

• (20.505, 21.495)