Exam 10: Statistical Inferences Based on Two Samples

Find a 90 percent confidence interval for the difference between the proportions of group l and group 2.Let p₁ represent the population proportion of the people in group 1 who are in favor of new packaging,and let p₂ represent the population proportion of the people in group 2 who are in favor of new packaging.

In testing the difference between two population variances,it is a common practice to compute the F statistic so that its value is always greater than or equal to one.

When comparing two independent population variances,the correct test statistic to use is __________.

In testing the equality of population variances,two assumptions are required: independent samples and normally distributed populations.

In a market research study conducted by a local winery on white wine preference,the following results were found.Of a sample of 500 men,120 preferred white wine.Of a sample of 500 women,210 preferred white wine.Set up the alternative hypothesis that will test the claim that the percentage of women who prefer white wine is 25 percent higher than the percentage of men who prefer white wine.

When testing a hypothesis about the mean of a population of paired differences in which two different observations are taken on the same units,the correct test statistic to use is _________.

In testing the difference between the means of two independent populations,if neither population is normally distributed,then the sampling distribution of the difference in means will be approximately normal,provided that the sum of the sample sizes obtained from the two populations is at least 30.

Zdravko Popovich,the mid-distance running coach for the Olympic team of an eastern European country,claims that his six-month training program significantly reduces the average time to complete a 1500-meter run.Five mid-distance runners were randomly selected.Their times (in minutes)for the 1500-meter run were recorded before and after six months of training under coach Popovich.The results are given below. At an alpha level of .05,can we conclude that there has been a significant decrease in the mean time?

A test of driving ability is given to a random sample of 10 student drivers before and after they complete a formal driver education course.Results follow. Calculate the mean difference between the before-class scores and the after-class scores.

Find a 95 percent confidence interval for μ₁ - μ₂,where Assume unequal variances.

A market research study conducted by a local winery on white wine preference found the following results.Of a sample of 500 men,120 preferred white wine.Of a sample of 500 women,210 preferred white wine.What do you conclude at α = .05 about the claim that the proportion of women who prefer white wine is 25 percent higher than the proportion of men who prefer white wine?

When comparing two population means based on independent random samples,the pooled estimate of the variance is used when there is an assumption of equal population variances.

Given the following information about a hypothesis test of the difference between two means based on independent random samples,what is the standard deviation of the difference between the two means? Assume that the samples are obtained from normally distributed populations having equal variances.

Parameters of the F distribution include:

In testing the difference between the means of two normally distributed populations using independent random samples,the correct test statistic to use is:

A coffee shop franchise owner is looking at two possible locations for a new shop.To help make a decision,he looks at the number of pedestrians that go by each of the two locations in one-hour segments.At location A,counts are taken for 35 one-hour units,with a mean number of pedestrians of 421 and a sample standard deviation of 122.At the second location (B),counts are taken for 50 one-hour units,with a mean number of pedestrians of 347 and a sample standard deviation of 85.Assume the two population variances are not known but are equal.Calculate the pooled estimate of σ².

The test of means for two related populations matches the observations (matched pairs)in order to reduce the ________________ attributable to the difference between individual observations and other factors.

The registrar at a state college is interested in determining whether there is a difference of more than one credit hour between male and female students in the average number of credit hours taken during a term.She selected a random sample of 60 male and 60 female students and observed the following sample information. What do you conclude at α = .01? Assume unequal variances.

The F statistic can assume either a positive or a negative value.

When testing the difference between two proportions selected from populations with large independent samples,the z test statistic is used.