Confidence Interval for Difference of Means

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.

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

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

• Sample mean

• t*

• Sample standard deviation

• Sample size

When road conditions are snowy, how much faster do people who have four wheel drive vehicles drive compared to those who have two wheel drive vehicles? 45 four wheel drive vehicles and 40 two wheel drive vehicles were clocked.

• Confidence Interval for a Population Mean

• Confidence Interval for a Proportion

• Confidence Interval for the Diff. Between 2 Means (Independent Samples)

• Confidence Interval for Paired Data (Dependent Samples)

A child psychologist wants to estimate the mean difference between the number of words children can recall when they hear them and the number of words they can recall when then see them on a written page. Fifty-two children were each read to and asked how many words they recalled and then they were asked to look at a book and asked how many words they recalled.

• Confidence Interval for a Population Mean

• Confidence Interval for a Proportion

• Confidence Interval for the Diff. Between 2 Means (Independent Samples)

• Confidence Interval for Paired Data (Dependent Samples)

• Confidence Interval for the Difference Between 2 Proportions

Seventy-four South Tahoe residents were asked how many cups of coffee they drank each week and how many glasses of water they drank each week. Estimate the mean difference between the average number of cups of coffee South Tahoe residents drink and the average number of glasses of water they drink.

• Confidence Interval for the Diff. Between 2 Means (Independent Samples)

• Confidence Interval for Paired Data (Dependent Samples)

• Hypothesis Test for a Population Proportion

• Hyp. Test for the Difference Between 2 Means (Independent Samples)

What do we use to estimate unknown parameters?

• Hypothesis Test

• Confidence Interval

• Trig Identity

• Guess and check

What interval should be used?

• 2 Sample t interval for means

• Paired t interval

• Paired t test

• 1 proportion z interval