Exam 13: Inference About Comparing Two Populat

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. {Worker Safety Narrative} What is the p -value of the test? Explain how to use it for testing the hypotheses.

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

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

TV Sex A survey of 1,500 Canadians reveals that 945 believe that there is too much sex on television. In a survey of 1,500 Americans, 810 believe that there is too much television sex. {TV Sex Narrative} Estimate with 99% confidence the difference in the proportion of Canadians and Americans who believe that there is too much sex on television.

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

If the sample sizes are large enough so the conditions are met, the difference between two sample proportions has an approximate ____________________ distribution.

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. {Clinic Waiting Time Narrative} Estimate with 95% confidence the ratio of the two population variances and interpret.

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

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. {Clinic Waiting Time Narrative} Can we infer at the 5% level of significance that the population variances differ?

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

We compare two population variances by examining their ____________________.

The F -distribution can only have non-negative values.

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

When comparing two population variances, we use the ratio rather than the difference .

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:

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. {Profit Margin Narrative} Estimate with 95% confidence the ratio of the two population variances.

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 {Antioxidants Narrative} Determine the rejection region for testing the equality of the two population variances at a = 0.05.

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

Mass Production Line A quality control examiner keeps a tally sheet of the number of acceptable and unacceptable products that come off two different production lines. The completed sheet is shown below. {Mass Production Line Narrative} Estimate with 95% confidence the difference in population proportions.

To estimate the ratio of the population variances you use the ____________________ of the ____________________ variances.