7.2

1. Researchers surveyed more than 230 American male weight lifters, ranging in age from 18 to 40, and found that 12% of them had used HGH, which has been banned in sports for more than 20 years now. The median usage time for those who reported HGH use was 23 weeks. Is each of the boldface numbers a parameter or a statistic?

A. 23 is a parameter, 12% is statistic.B. The two boldface numbers are parameters.C. 12% is a parameter, 23 is statistic.D. 12% and 23 are statistics.

2. Scores on the Critical Reading part of the SAT exam in a recent year were roughly Normal with mean 501 and standard deviation 112. You choose an SRS of 100 students and average their SAT Critical Reading scores. If you do this many times, the mean of the average scores you get will be close to

A. 501/√100 = 50.1.B. 501.C. 501/100 = 5.01.

3. Scores on the Critical Reading portion of the SAT college entrance test in a recent year were roughly Normal with mean 501 and standard deviation 112. You choose an SRS of 100 students and average their SAT scores. If you do this many times, the standard deviation of the average scores you get will be close to

A. 112/√100 = 11.2.B. 112.C. 112/√100 = 1.12.

0.529

1.226

0.993

5. The average age of residents in a large residential retirement community is 69 years with standard deviation 5.8 years. A simple random sample of 100 residents is to be selected, and the sample mean age of these residents is to be computed.Reference: Ref 11-3

We know the random variable has approximately a Normal distribution because of

A. the population we're sampling from has a Normal distribution.B. the 68–95–99.7 rule.C. the central limit theorem.D. the law of large numbers.

6. The central limit theorem says that when a simple sample of size n is drawn from any population with mean μ and standard deviation σ, then when n is sufficiently large

A. the distribution of the sample mean is approximately Normal.B. the distribution of the population is approximately Normal.C. the standard deviation of the sample mean is σ2/n.D. the distribution of the sample mean is exactly Normal.

7. 71. To give a 99.9% confidence interval for a population mean , you would use the critical value

A. z* = 2.576.B. z* = 1.960.C. z* = 3.291.

2. You plan to construct a confidence interval for the mean μ of a Normal population with (known) standard deviation σ. Which of the following will reduce the size of the margin of error?

A. Use a lower level of confidence.B. Increase the sample size.C. Reduce σ.D. All of the above.

3. A level 0.95 confidence interval is

A. an interval computed from sample data by a method guaranteeing that the probability the interval computed contains the parameter of interest is 0.95.B. an interval computed from sample data by a method that has probability 0.95 of producing an interval containing the true value of the parameter of interest.C. any interval with margin of error ± 0.95.D. an interval with margin of error ± 0.95, which is also correct 95% of the time.

4. The scores of a certain population on the Wechsler Intelligence Scale for Children (WISC) are thought to be Normally distributed with mean μ and standard deviation σ = 10. A simple random sample of 25 children from this population is taken and each is given the WISC test. The mean of the 25 scores is = 104.32.

Based on these data, a 95% confidence interval for μ is

A. 104.32 ± 3.29.B. 104.32 ± 19.60C. 104.32 ± 0.78.D. 104.32 ± 3.92.

5. Twenty-five seniors from a large metropolitan area school district volunteer to allow their Math SAT test scores to be used in a study. These 25 seniors had a mean Math SAT score of = 450. Suppose we know that the standard deviation of the population of Math SAT scores for seniors in the district is σ = 100. Assuming the population of Math SAT scores for seniors in the district is approximately Normally distributed, a 90% confidence interval for the mean Math SAT score μ for the population of seniors computed from these data is

A. 450 ± 32.9.B. 450 ± 39.2.C. 450 ± 164.5.D. not trustworthy.

7.8The critical value z* for confidence level C = 97.5% is not in Table C.

1. Use software or Table A of standard Normal probabilities to find z*.

A. z* = 1.96B. z* = 2.24C. z* = 2.32D. z* = 0.838

4. The coach of a college men’s soccer team records the resting heart rates of the 27 team members. You should not trust a confidence interval for the mean resting heart rate of all male students at this college based on these data because

A. the members of the soccer team can't be considered a random sample of all students.

B. with only 27 observations, the margin of error will be large.

C. heart rates may not have a Normal distribution.

What critical value t* from Table C would you use for a confidence interval for the mean of the population in each of the following situations?

5. A 90% confidence interval based on n = 10 observations.

A. 1.833

B. 1.812

C. 1.383

D. 1.372

6. A 90% confidence interval from an SRS of 20 observations.

A. 2.093

B. 1.729

C. 1.725

D. 1.328

7. A 95% confidence interval from a sample of size 7.

A. 2.365

B. 2.306

C. 1.960

D. 2.447

8. Data on the blood cholesterol levels of 10 rats (milligrams per deciliter of blood) give x = 85 and s = 12. A 99% confidence interval for the mean blood cholesterol of rats is

A. 76.4 to 93.6.

B. 72.7 to 97.3.

C. 73.0 to 97.0.