Review Units 7.1-7.4

An increase in sample size produces

• a smaller margin of error.

• a larger margin of error.

• does not affect margin of error.

• a biased margin of error

Increasing the confidence level results in

• a smaller margin of error.

• a larger margin of error.

• no change in the margin of error.

• a biased interval.

Increasing the confidence level results in

• an increase in the percent hit (capture rate).

• a decrease in the percent hit (capture rate)

• no change in the percent hit (capture rate)

• a biased percent hit (capture rate)

Which of the following statements are true about confidence intervals?

• Confidence intervals always capture the true population parameter.

• The middle of the confidence interval is the most likely value for the population parameter.

• Confidence intervals provide a range of plausible values for a population parameter.

• All samples of a population should produce the exact same confidence intervals for the parameter of that population.

A 95% confidence interval for a population parameter is (.33, .39). What was the point estimate and margin of error for this interval?

• point estimate = .36; margin of error = .03

• point estimate = .36; margin of error = .06

• point estimate = .33; margin of error = .06

• point estimate = .39; margin of error = .03

• (.45, .485)

• (.415, .485)

• (.45, .035)

• (.10, .80)

A 90% confidence interval for a population proportion is (.25, .35). Which of the following is not a correct conclusion based on the interval?

• 20% is not a plausible value for the population proportion.

• 30% is a plausible value for the population proportion.

• About 90% of such intervals will capture the true population parameter.

• Since 30% is in the middle of the interval, it must be equal to the population parameter.

You are trying to estimate the proportion of HHS students who like oatmeal. You randomly sample 12 students and 4 students say yes. Can this data be used to construct a confidence interval using the normal model?

• Yes because the data came from a random sample.

• Yes because some students said yes and some said no.

• No because the sample size is not large enough to have at least 10 who said yes and 10 who said no.

• No because the sample was not selected randomly.

 You ask 50 randomly selected seniors if they like oatmeal. 12 said yes. Which of the following equations would correctly produce a 90% confidence interval for the true proportion of seniors who like oatmeal?

Using the sample of 50, the 95% confidence interval for the true proportion of students who like oatmeal is (.122, .358). Does this interval provide convincing evidence that fewer than half of students like oatmeal?

• Yes, because the entire interval is below 50%. According to the interval, 50% is not a plausible value.

• No, oatmeal is tasty and a good warm breakfast on a cold day.

• No, because you can put fruit and cinnamon in oatmeal and people will like it better.

• No, oats are heart healthy, full of fiber, and gluten free. More students should eat them.