CHAPTER 12

41. To generate a confidence interval that possesses a desired width, yet complies with a desired level of confidence, refer to formulas (in other books) for the selection of an appropriate

a) confidence interval.

b) interval width.

c) level of confidence.

d) sample size.

42. A false 95 percent confidence interval would be produced if, in fact, the one observed sample mean

a) coincides with the unknown population mean.

b) deviates one-half of a standard error unit above the unknown population mean.

c) deviates one and one-half standard error units below the unknown population mean.

d) deviates three standard error units above the unknown population mean.

43. To understand why confidence intervals work, it's important to view the observed sample mean as originating from a

a) single random sample that reflects the unknown population mean.

b) sampling distribution that is centered about the unknown population mean.

c) population that is centered about the unknown population mean.

d) confidence interval that will be true 95 percent of the time.

44. Specify which one of the following 95 percent confidence intervals would bemost preferable, given that you wish to demonstrate that a summer workshop increases GPAs.

a) 2.70 to 3.30

b) 2.50 to 3.50

c) 2.90 to 3.40

d) 2.80 to 3.40

45. A pollster reports, with 95 percent confidence, that between 55 and 61 percent of all Americans favor mandatory drug testing's for employees in positions of public trust (bus drivers, airline pilots, etc). The point estimate for the unknown population proportion (who favor mandatory drug testing) equals

a) 55 percent.

b) 58 percent.

c) 61 percent.

d) some unknown percent.

46. Often encountered in national polls are sample sizes of about

a) 10,000

b) 1,500

c) 500

d) 100

47. Prior to attending college, randomly selected college-bound students participate in a summer workshop on the development of good study habits. Subsequently, at the end of their first year in college, they showed a dramatic increase in grade point averages, relative to the national average of 2.75, as revealed by a 95 percent confidence interval of 2.90 to 3.30. This confidence interval signifies that

a) every student who participated in the summer workshop had a GPA between 2.90 and 3.30.

b) about 95 percent of all students who participated in the summer workshop had GPAs between 2.90 and 3.30.

c) the true population mean (for all students who could conceivably take the summer workshop) is between 2.90 and 3.30.

d) we can be reasonably confident that the true population mean (for all students who could conceivably take the summer workshop) is between 2.90 and 3.30.

48. Pollsters tend to use larger samples than researchers for a number of reasons including the notion that, in surveys, samples

a) can't ever be too large.

b) often contain observations that are relatively easy to obtain.

c) both a and b

d) neither a nor b

49. Given a sample mean of 130 and a sample standard deviation of 20, a point estimate of the unknown population mean would equal

a) 130

b) 130/20

c) 130 plus or minus 20

d) approximately 90 to 170

50. Consider the use of a

a) hypothesis test whenever a confidence interval has been constructed.

b) hypothesis test whenever you suspect the null hypothesis to be true.

c) confidence interval whenever the null hypothesis has been retained.

d) confidence interval whenever the null hypothesis has been rejected.