Exam 13: Inference About Comparing Two Populations, Part 2

When testing the equality of two population variances the number in the null hypothesis is 0.

In constructing a confidence interval estimate for the difference between two population proportions, we ____________________ (always/sometimes/never) pool the population proportions.

Can we infer at the 99% significance level that the proportion of Canadians and Americans who believe that there is too much sex on television differ?

In comparing two population means the statistic under consideration is .

The test statistic for testing for the equality of two population variances has a(n) ____________________ distribution.

The pooled proportion estimate is used when the proportion of successes from sample 1 equals the proportion of successes from sample 2.

The ratio of two independent chi-squared variables divided by their degrees of freedom is:

The pooled proportion estimate is used when the null hypothesis states that the two population proportions differ by some non-zero number.

Profit Margin: An investor is considering two types of investment. She is quite satisfied that the expected profit margin on Investment 1 is higher than the expected profit margin on Investment 2. However, she is quite concerned that the risk associated with Investment 1 is higher than that of Investment 2. To help make her decision, she randomly selects seven monthly profit margins on investment 1 and ten monthly profit margins on investment 2. She finds that the sample variances of Investments 1 and 2 are 225 and 118, respectively. -Can she infer at the 5% significance level that the population variance of investment 1 exceeds that of investment 2?

Antioxidants: A food processor wants to compare two antioxidants for their effects on retarding spoilage. Suppose 16 cuts of fresh meat are treated with antioxidant A and 16 are treated with antioxidant B, and the number of hours until spoilage begins is recorded for each of the 32 cuts of meat. The results are summarized in the table below -State the null and alternative hypotheses for determining if the population variances differ for Antioxidants A and B.

Pooling is made possible by hypothesizing (under the null hypothesis) that p₁ = p₂.

Clinic Waiting Time: In a random sample of 20 patients who visited a clinic at Medical Center 1, a researcher found that the variance of the waiting time (in minutes) was 128.0. In a random sample of 15 patients in the clinic of Medical Center 2, the researcher found the variance to be 178.8. -Can we infer at the 5% level of significance that the population variances differ?

In constructing a confidence interval estimate for the difference between two population proportions, we:

The pooled proportion estimate is used when the null hypothesis states that the two population proportions differ by ____________________.

Worker Safety: An OSHA agent wanted to determine if efforts to promote safety have been successful. By checking the records of 250 workers, he found that 30 of them suffered either minor or major injuries that year. A random sample of 400 workers last year revealed that 80 suffered some form of injury. -What is the p-value of the test? Explain how to use it for testing the hypotheses.

In testing for the equality of two population variances, when the populations are normally distributed, the 10% level of significance has been used. To determine the rejection region, it will be necessary to refer to the F table corresponding to an upper-tail area of:

Senatorial Election: A political poll immediately prior to a senatorial election reveals that 145 out of 250 male voters and 105 out of 200 female voters intend to vote for the Democrat candidate. -Explain how to use the interval estimate to test the hypotheses.

Which of the following statements is correct regarding the percentile points of the F-distribution?

In constructing a confidence interval estimate for the difference between two population proportions, we ____________________ (always/sometimes/never) pool the population proportions.

When the data from two populations are ____________________ the parameter to be tested and estimated is the difference between the two population proportions.