Question 1

A company believes that it controls more than 30% of the total market share for one of its products.To prove this belief, a random sample of 144 purchases of this product is contacted.It is found that 50 of the 144 purchased this company's brand of the product.If a researcher wants to conduct a statistical test for this problem, the observed z value would be ___.

Accepted Answer

A) 0.05 
B) 0.103 
C) 0.35 
D) 1.24 
E) 1.67

Question 2

In performing a hypothesis test where the null hypothesis is that the population mean is 4.8 against the alternative hypothesis that the population mean is not equal to 4.8, a random sample of 25 items is selected.The sample mean is 4.1 and the sample standard deviation is 1.4.It can be assumed that the population is normally distributed.The observed "t" value for this problem is ___.

Accepted Answer

A) -12.5 
B) 12.5 
C) -2.5 
D) -0.7 
E) 0.7

Question 3

Ophelia O'Brien, VP of Consumer Credit of Credit First Banks (CFB), monitors the default rate on personal loans at the CFB member banks.One of her standards is "no more than 5% of personal loans should be in default." On each Friday, the default rate is calculated for a sample of 500 personal loans.Last Friday's sample contained 30 defaulted loans.Using $\alpha$= 0.10, the critical z value is ___.

Accepted Answer

A) 1.645 
B) -1.645 
C) 1.28 
D) -1.28 
E) 2.28

Question 4

In a two-tailed hypothesis about a population mean with a sample size of 100 and α = 0.05, the rejection region would be ___.

Accepted Answer

A) z > 1.64 
B) z > 1.96 
C) z  1.96 
D) z  1.64 
E) z  2.33

Question 5

Suppose you are testing the null hypothesis that a population mean is less than or equal to 80, against the alternative hypothesis that the population mean is greater than 80.If the sample size is 49 and alpha = .10, the critical value of z is ___.

Accepted Answer

A) 1.645 
B) -1.645 
C) 1.28 
D) -1.28 
E) 2.33

Question 6

The diameter of 3.5 centimetre discs is normally distributed.Periodically, quality control inspectors at Winnipeg Discs randomly select a sample of 16 discs.If the mean diameter of the discs is too large or too small the disc punch is shut down for adjustment; otherwise, the punching process continues.The last sample showed a mean and standard deviation of 3.49 and 0.08 centimetres, respectively.Using $\alpha$ = 0.05, the appropriate decision is ___.

Accepted Answer

A) reject the null hypothesis and shut down the punch 
B) reject the null hypothesis and do not shut down the punch 
C) do not reject the null hypothesis and shut down the punch 
D) do not reject the null hypothesis and do not shut down the punch 
E) do nothing

Question 7

In performing hypothesis tests about the population mean, the population standard deviation should be used if it is known.If it is not known, a t test can be used to test the mean if ___.

Accepted Answer

A) the sample size is at least thirty 
B) the sample is random 
C) the population mean is known 
D) the population is normally distributed 
E) the population is chi-square distributed

Question 8

The null and the alternative hypotheses must be mutually exclusive and collectively exhaustive.

Accepted Answer

A) True 
 B)False

Question 9

A company believes that it controls more than 30% of the total market share for one of its products.To prove this belief, a random sample of 144 purchases of this product is contacted.It is found that 50 of the 144 purchased this company's brand of the product.If a researcher wants to conduct a statistical test for this problem, the test would be ___.

Accepted Answer

A) a one-tailed test 
B) a two-tailed test 
C) an alpha test 
D) a finite population test 
E) a finite sample test

Question 10

A null hypothesis is p > 0.65.To test this hypothesis, a sample of 400 is taken and alpha is set at 0.05.If the true proportion is p = 0.60, what is the probability of a Type II error?

Accepted Answer

A) 0.17 
B) 0.45 
C) 0.95 
D) 0.67 
E) 0.33

Question 11

A company believes that it controls more than 30% of the total market share for one of its products.To prove this belief, a random sample of 144 purchases of this product is contacted.It is found that 50 of the 144 purchased this company's brand of the product.If a researcher wants to conduct a statistical test for this problem, the alternative hypothesis would be ___.

Accepted Answer

A) the population proportion is less than 0.30 
B) the population proportion is greater than 0.30 
C) the population proportion is not equal to 0.30 
D) the population mean is less than 40 
E) the population mean is greater than 40

Question 12

When a true null hypothesis is rejected, the researcher has made a Type I error.

Accepted Answer

A) True 
 B)False

Question 13

Ophelia O'Brien, VP of Consumer Credit of Credit First Banks (CFB), monitors the default rate on personal loans at the CFB member banks.One of her standards is "no more than 5% of personal loans should be in default." On each Friday, the default rate is calculated for a sample of 500 personal loans.Last Friday's sample contained 30 defaulted loans.Using$\alpha$= 0.10, the appropriate decision is ___.

Accepted Answer

A) reduce the sample size 
B) increase the sample size 
C) reject the null hypothesis 
D) do not reject the null hypothesis 
E) do nothing

Exam 9: Statistical Inference: Hypothesis Testing for Single Populations

In a two-tailed hypothesis about a population mean with a sample size of 100 and α = 0.05, the rejection region would be ___.

Suppose you are testing the null hypothesis that a population mean is less than or equal to 80, against the alternative hypothesis that the population mean is greater than 80.If the sample size is 49 and alpha = .10, the critical value of z is ___.

In performing hypothesis tests about the population mean, the population standard deviation should be used if it is known.If it is not known, a t test can be used to test the mean if ___.

The null and the alternative hypotheses must be mutually exclusive and collectively exhaustive.

A null hypothesis is p > 0.65.To test this hypothesis, a sample of 400 is taken and alpha is set at 0.05.If the true proportion is p = 0.60, what is the probability of a Type II error?

When a true null hypothesis is rejected, the researcher has made a Type I error.