[PSYCH STATS] Chapter 8 Review

A researcher expects a treatment to produce a decrease in the population mean. The treatment is evaluated using a one-tailed hypothesis test. Which z-scores would lead us to reject the null hypothesis with α = .05? I. z = -1.75 II. z = 1.75 III. z = -1.6 IV. z = 1.6 a. I only b. I and II only c. II, III, and IV only d. None of the four

A

What would be the result of setting an alpha level extremely small? a. There would be almost no risk of a Type I error. b. It would be very difficult to reject the null hypothesis. c. Neither a nor b d. Both a and b

D

Which of the following is a common limitation of hypothesis testing? a. Conclusions are made about the data set rather than about the hypothesis itself. b. Demonstrating a significant treatment effect does not necessarily indicate a substantial treatment effect. c. Hypothesis testing loses its effectiveness for small samples. d. Both a and b

D

A researcher administers a treatment to a sample of n = 100 participants and uses a hypothesis test to evaluate the effect of the treatment. The hypothesis test produces a z-score of z = 2.1. Assuming that the researcher is using a two-tailed test, what should the researcher do? a. The researcher should reject the null hypothesis with α = .05, but not with α = .01. b. The researcher should reject the null hypothesis with either α = .05 or α = .01. c. The researcher should fail to reject the null hypothesis with either α = .05 or α = .01. d. Cannot answer without additional information.

A

A random sample is selected from a normal population with a mean of μ = 200 and a standard deviation of σ = 12. After a treatment is administered to the individuals in the sample, the sample mean is found to be M = 196. How large a sample is necessary for this sample mean to be statistically significant using a two-tailed test with α = .05? a. 30 b. 35 c. 40 d. 70

B

Assuming a normal distribution, which of the following would call for a one-tailed hypothesis test rather than a two-tailed test? a. Determining if attending Harvard influences IQ b. Determining if driving a red car increases the number of speeding tickets per year c. Determining if being male influences height d. Determining if being a teenager influences the number of hours of sleep per night

B

If other factors are held constant, then how does the sample size affect the likelihood of rejecting the null hypothesis and the value for Cohen's d? a. A larger sample size increases the likelihood of rejecting the null hypothesis and increases the value of Cohen's d. b. A larger sample size increases the likelihood of rejecting the null hypothesis but does not change the value of Cohen's d. c. A larger standard deviation decreases the likelihood of rejecting the null hypothesis but increases the value of Cohen's d. d. A larger standard deviation decreases the likelihood of rejecting the null hypothesis and does not change the value of Cohen's d.

B

What is the primary concern when selecting an alpha value? a. To make the null hypothesis easy to test b. To minimize Type I errors c. To minimize Type II errors d. To make z-scores easy to calculate

B

Which of the following is not an assumption for hypothesis tests with z-scores? a. random sampling b. small standard deviations c. normal sampling distribution d. independent observations

B

Which of the following correctly describes the effect that decreasing sample size and decreasing the standard deviation have on the power of a hypothesis test? a. A decrease in sample size will decrease the power, but a decrease in standard deviation will increase the power. b. Both will increase the power. c. A decrease in sample size will increase the power, but a decrease in standard deviation will decrease the power d. Both will decrease the power.

A

A researcher is evaluating the influence of a treatment using a sample selected from a normally distributed population with a mean of μ = 30 and a standard deviation of σ = 3. The researcher expects a 1-point treatment effect and plans to use a two-tailed hypothesis test with α = 0.05. Compute the power of the test if the researcher uses n = 9 individuals. a. 17% b. 50% c. 83% d. Nearly 100%

A

A treatment is administered to a sample selected from a population with a mean of μ = 40 and a standard deviation of σ = 6.25. After treatment, the sample mean is M = 45. Based on this information, the effect size as measured by Cohen's d can be classified as which of the following? a. Large effect b. Medium effect c. Small effect d. No effect

A

In a normal sample distribution with n = 16, the null hypothesis is rejected. If the sample size is changed to 64 with all other factors staying the same, what happens to the z-score and the decision about the null hypothesis? a. The z-score is doubled, and the null hypothesis is still rejected. b. The z-score is multiplied by 6, and the null hypothesis is still rejected. c. The z-score is doubled, and we fail to reject the null hypothesis. d. The z-score is multiplied by 6, and we fail to reject the null hypothesis.

A

What is a Type I error? a. When a researcher rejects a null hypothesis that is actually true b. When a researcher fails to rejects a null hypothesis that is actually false c. When a researcher does not set an alpha level high enough d. When a researcher sets an alpha level too high

A

A study is conducted to see if teenagers drive at faster average speeds than the general population of drivers. The average speed of the driving population is 35 mph. The null hypothesis is H0: μaverage driving speed of teenagers = 35 mph. What is the alternative hypothesis? a. H1: μdriving speed of teenagers = 35 mph b. H1: μdriving speed of teenagers ≠ 35 mph c. H1: μdriving speed of teenagers > 35 mph d. H1: μdriving speed of teenagers < 35 mph

B

A random sample is normally distributed. If all values in the sample and all values in the population are multiplied by 2, what is the impact on Cohen's d? a. Decreases b. Increases c. Stays the same d. It is impossible to tell

C

A research report summarizes the results of the hypothesis test by stating, "z = 3.11, p < .01." Which of the following is a correct interpretation of this report? a. The null hypothesis was not rejected, and the probability of a Type I error is less than .01. b. The null hypothesis was not rejected, and the probability of a Type II error is less than .01. c. The null hypothesis was rejected, and the probability of a Type I error is less than .01. d. The null hypothesis was rejected, and the probability of a Type II error is less than .01.

C

Which of the following are correct ways of defining the power of a statistical test?I. The probability that the test will correctly reject a false null hypothesisII. The probability that the test will result in a Type II errorIII. The probability that the test will not result in a Type II error a. I only b. I and II c. I and III d. II only

C

Which of the following explains why it is easier to reject the null hypothesis with a one-tailed test than with a two-tailed test with all the same parameters? a. Because the standard deviation in a one-tailed test is larger than that for a two-tailed test b. Because z-scores are calculated differently in a one-tailed test c. Because the critical region is all on one side in a one-tailed test and needs to be split between the two tails in a two-tailed test d. Because a two-tailed test uses a bimodal distribution

C

Which of the following is not a step in a hypothesis test? a. State the null hypothesis about a population. b. Set the alpha level. c. If the sample data is not located in the critical region, we accept the null hypothesis. d. If the sample data is located in the critical region, we reject the null hypothesis.

C