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Discrete Components Inc. manufactures a line of electrical resistors. Presently, the carbon composition line is producing 100 ohm resistors. The population variance of these resistors “must not exceed 4” to conform to industry standards. Periodically, the quality control inspectors check for conformity by randomly select 10 resistors from the line, and calculating the sample variance. The last sample had a variance of 4.36. Assume that the population is normally distributed.

increase the sample size

reduce the sample size

reject the null hypothesis

do not reject the null hypothesis

1.27

3.15

4.87

3.87

1.96

Independent random samples selected from two normal populations produced the sample means and standard deviations shown below:

(-5.64, 0.04)

(-4.13, -1.47)

(-5.19, -0.41)

(-6.18, 0.58)

A researcher wants to estimate the difference in population proportions for two populations using a 98% confidence interval. In a sample of 900 persons from the first population, 288 possessed the characteristic of interest. In a sample of 800 from the second population, 240 possessed the characteristic of interest. A 98% confidence interval for the difference in the population proportions is ___.

{0.0323, -0.0723}

{0.0423, 0.0723}

{0.0223, 0.0923}

{-0.0323, 0.0723}

{0.0323, 0.0723}

Restaurateur Denny Valentine is evaluating two sites, Raymondville and Rosenberg, for his next restaurant. He wants to prove that Raymondville residents (population 1) dine out more often than Rosenberg residents (population 2). Denny commissions a market survey to test this hypothesis. The market researcher used a random sample of 64 families from each suburb, and reported the following: x1= 16 times per month and x2= 14 times per month. Assume that σ1 = 4 and σ2 = 3. With α = .01, the appropriate decision is ___.

reject the null hypothesis σ1 < σ2 accept the alternate hypothesis μ1 – μ2 > 0

reject the alternate hypothesis n1 = n2 = 64

do not reject the null hypothesis μ1 – μ2 = 0

A researcher wants to conduct a before/after study on 11 subjects to determine if a treatment results in any difference in scores. The null hypothesis is that the average difference is zero while the alternative hypothesis is that the average difference is not zero. Scores are obtained on the subjects both before and after the treatment. After subtracting the after scores from the before scores, the average difference is computed to be 2.40 with a sample standard deviation of 1.21. Assume that the differences are normally distributed in the population. The observed t value for this test is ___.

–21.82

–6.58

–2.4

1.98

2.33

A researcher is conducting a matched-pairs study. She gathers data on each pair in the study resulting in:

1.3

1.14

1.04

1.02

1.47

Assume that the data are normally distributed in the population. The degrees of freedom in this problem are ___.

The answer is 4

4

8

5

The dean of a business school claims that the average starting salary of its graduates is more than 60 ($thousands). It is known that the population standard deviation is 10 ($thousands). Sample data on the starting salaries of 64 randomly selected recent graduates yielded a mean of 62 ($thousands). What is the value of the sample test statistic?2.001.801. 851.651.60