20. Assume that blood pressure readings are normally distributed with a mean of 117 and a standard deviation of 9.6. If 144 people are randomly selected, find the probability that their mean blood pressure will be less than 119.

0.9998

0.8615

0.0062

0.9938

21. When 390 junior college students were surveyed,115 said that they have previously owned a motorcycle. Find a point estimate for p, the population proportion of students who have previously owned a motorcycle.

0.295

0.705

0.228

0.418

22. Determine the critical value z/2 that corresponds to the given level of confidence.

90%

1.34

1.28

1.645

0.82

23. A simple random sample of size n < 30 has been obtained. From the boxplot, judge whether a t-interval should be constructed.

No, there are outliers and the data are not normally distributed but right skewed

No, though there are no outliers, the data are not normally distributed but right skewed

Yes; the data are normally distributed and there are no outliers

No; the data are normally distributed, but there are outliers

24. Which of the following is not a characteristic of Students' t-distribution?

mean of 1

symmetric distribution

For large samples, the t and z distributions are nearly equivalent.

depends on degrees of freedom.

25. Find the critical t-value that corresponds to 90% confidence and n = 15.

2.624

2.145

1.761

1.345

26. Construct a 90% confidence interval for the population mean, . Assume the population has a normal distribution. A sample of 15 randomly selected math majors has a grade point average of 2.86 with a standard deviation of 0.78. Round to the nearest hundredth.

(2.37, 3.56)

(2.41, 3.42)

(2.28, 3.66)

(2.51, 3.21)

27. The null and alternative hypotheses are given. Determine whether the hypothesis test is left-tailed, right-tailed, or two-tailed and the parameter that is being tested.

H0: = 8.5

H1: < 8.5

Right-tailed,

Right-tailed,

Left-tailed, s

Left-tailed,

28. True or False: Type I and Type II errors are independent events.

Group of answer choices

False

True

29. A candidate for state representative of a certain state claims to be favored by at least half of the voters. If a hypothesis test is performed, how should you interpret a decision that rejects the null hypothesis?

There is sufficient evidence to support the claim p 0.5.

There is not sufficient evidence to reject the claim p 0.5.

There is not sufficient evidence to support the claim p 0.5.

There is sufficient evidence to reject the claim p 0.5.