Confidence Intervals for Difference of Means

Which of the following does NOT have an affect on the width of a confidence interval?

• Sample mean

• t*

• Sample standard deviation

• Sample size

How much faster do people who own sports cars drive on the freeway compared to people who own economy cars.  520 sports cars and 890 economy cars were clocked as they passed by on the freeway. Which procedure is appropriate?

• t interval for means

• t interval for difference of means

• z interval for proportions

• z interval for difference of proportions

If p₁ - p₂ = 0, is in the 90% confidence interval, what can we conclude at α = 0.10?

• Reject H₀, there is sufficient evidence to conclude H_a

• Reject H₀, there is NOT sufficient evidence to conclude H_a

• Fail to reject H₀, there is sufficient evidence to conclude H_a

• Fail to reject H₀, there is NOT sufficient evidence to conclude H_a

A two-tailed hypothesis test with H₀: μ₁-μ₂ = 0 produced a p-value of 0.08.  Which of the following must be true?

• The 90% confidence interval will NOT contain 0.

• The 95% confidence interval will NOT contain 0.

• The 99% confidence interval will NOT contain 0.

• All the confidence intervals listed will contain 0.

• A

• B

• C

• D

• E

How much more time do men spend listening to music compared to women?  52 men and 52 women were surveyed. Which procedure is appropriate?

• t interval for difference of means

• t test for difference of means

• z interval for difference of proportions

• z test for difference of proportions

Which of the following is an example of an interval estimate?

• point estimate 

• critical value

• confidence interval

• statistic

A __________ gives an interval of plausible values for the _____________. 

• confidence interval, statistic

• point estimate, parameter

• point estimate, statistic

• confidence interval, parameter

Which confidence would result in a wider interval (assuming nothing else changed), 91% or 97%?

• 97%, z* is larger for higher confidence intervals

• 97%, the standard error is larger for higher confidence intervals

• 91%, z* is larger for lower confidence intervals

• 91%, the standard error is smaller for lower confidence intervals