Exam 2 Review

The mean of 16 subjects on an attitude scale after receiving a persuasive message is 38.4. The mean for the same subjects before receiving the message was 32.6. If the appropriate standard error of the difference is 9.7 and the critical value needed to reject the null hypothesis is 2.145, the researcher should conclude that: A) the message makes no change in people's attitudes. B) the message changes people's attitudes. C) none of the above.

A) the message makes no change in people's attitudes.

What value is expected for the t statistic when the null hypothesis is true? A. 0 B. 1 C. 1.96 D. t > 1.96

A. 0

The 95% confidence interval for the mean of a population is 25.8 to 40.1. Which of the following cannot be the 99% confidence interval for the same population mean? A) 20.6 to 45.3 B) 27.0 to 38.9 C) Both of the above D) Neither of the above

B) 27.0 to 38.9

If we are testing a hypothesis about the difference between two population means and we switch from the .05 criterion of significance to the .01 criterion, what happens to the probabilities of a Type I error? B) The probability of a Type I error becomes smaller. C) The probability of a Type I error becomes larger D) Cannot be determined.

B) The probability of a Type I error becomes smaller.

As the size of the sample increases, the standard error of the mean: A) becomes larger. B) becomes smaller. C) remains the same. D) cannot be determined from the information given.

B) becomes smaller.

A Type I error occurs when the researcher: A) rejects a false null hypothesis. B) rejects a true null hypothesis. C) retains a false null hypothesis. D) retains a true null hypothesis.

B) rejects a true null hypothesis.

If other factors are held constant, what is the effect of increasing the sample variance? A. It will increase the estimated standard error and increase the likelihood of rejecting H0. B. It will increase the estimated standard error and decrease the likelihood of rejecting H0. C. It will decrease the estimated standard error and increase the likelihood of rejecting H0. D. It will decrease the estimated standard error and decrease the likelihood of rejecting H0.

B. It will increase the estimated standard error and decrease the likelihood of rejecting H0.

When you are using a one-sample t test, the degrees of freedom are A. N. B. N - 1. C. N + 1. D. N - 2.

B. N - 1

When you state a one-tailed test for an experimental treatment that aims to decrease anxiety, what does the appropriate null hypothesis state? A. The experimental treatment has no effect on the behavior B. The experimental treatment has the opposite effect what was expected C. The experimental treatment has a small effect in the expected direction D. The null hypothesis includes (a) and (b) above E. The null hypothesis includes (a) and (b) and (c) above

B. The experimental treatment has the opposite effect what was expected

If a sample of 100 people has a mean of 34 and a standard deviation of 7, the estimated standard error of the mean is: A) .07 B) .34 C) .7 D) 3.4

C) .7

The standard error of the mean tells us: A) the variability of means of samples of the same size drawn from the same population. B) how trustworthy a single mean is as an estimate of the corresponding population mean. C) both of the above. D) neither of the above.

C) both of the above.

A Type II error occurs when the researcher: A) rejects a false null hypothesis. B) rejects a true null hypothesis. C) retains a false null hypothesis. D) retains a true null hypothesis.

C) retains a false null hypothesis.

The critical t value for a one-group experiment will never be: A) less than zero. B) less than 2. C) smaller than the corresponding critical z. D) larger than the corresponding critical z.

C) smaller than the corresponding critical z.

If other factors are held constant, what is the effect of increasing the sample size? A. It will increase the estimated standard error and increase the likelihood of rejecting H0. B. It will increase the estimated standard error and decrease the likelihood of rejecting H0. C. It will decrease the estimated standard error and increase the likelihood of rejecting H0. D. It will decrease the estimated standard error and decrease the likelihood of rejecting H0.

C. It will decrease the estimated standard error and increase the likelihood of rejecting H0.

Which of the following statements is true about t distributions? A. There are exactly 10 categories of t distributions. B. For any given sample size, there are between two and N - 1 appropriate t distributions. C. The larger the sample size, the more a t distribution resembles a standard normal distribution. D. t distributions are generally bimodal.

C. The larger the sample size, the more a t distribution resembles a standard normal distribution.

If we have run a t test with 35 observations and have found a t of 3.60, which is significant at the .05 level, we would write A. t(35) = 3.60, p < .05. B. t(34) = 3.60, p > .05. C. t(34) = 3.60, p < .05. D. t(35) = 3.60, p < 05.

C. t(34) = 3.60, p < .05.

The power of a statistical test is equal to the probability of: A) retaining the null hypothesis when it is true. B) rejecting the null hypothesis when it is true. C) retaining the null hypothesis when it is false. D) rejecting the null hypothesis when it is false.

D) rejecting the null hypothesis when it is false.

When drawing inferences about the mean of one population, the correct statistical model to use is: A) the normal curve. B) the t distributions. C) the t distributions if the population standard deviation is known and the normal curve if the population standard deviation is not known. D) the normal curve if the population standard deviation is known and the t distributions if the population standard deviation is not known.

D) the normal curve if the population standard deviation is known and the t distributions if the population standard deviation is not known.

For the matched t test, the degrees of freedom are: A) the number of scores. B) the number of pairs. C) the number of scores minus 1. D) the number of pairs minus 1.

D) the number of pairs minus 1.

What is a Type I error? A. Incorrectly translating theory into hypotheses B. Failing to accept the alternative hypothesis when it is true C. Using an inappropriate test statistic for the hypotheses stated D. Rejecting the null hypothesis when it is true

D. Rejecting the null hypothesis when it is true

Which of the following does NOT directly affect the magnitude of t? A. The mean difference. B. The sample variance (s^2). C. The sample size (N). D. The population variance (σ^2).

D. The population variance (σ^2).

Suppose that we know that the sample mean is 18 and the population standard deviation is 3. We want to test the null hypothesis that the population mean is 20. In this situation we would A. reject the null hypothesis at α = .05. B. reject the null hypothesis at α = .01. C. retain the null hypothesis. D. We cannot solve this problem without knowing the sample size.

D. We cannot solve this problem without knowing the sample size.

All of the following increase the magnitude of the t-statistic/chances of rejecting H0 EXCEPT: A. a greater difference between the sample mean and the population mean. B. an increase in sample size. C. a decrease in sample variance. D. a smaller significance level (α).

D. a smaller significance level (α).

A sample of N = 100 has a mean of 34.7. The population standard deviation is known to be 6.0. Which of the following null-hypothesized values of the population mean should be rejected using the .05 criterion of significance? A) 33.8 B) 35.0 C) 35.5 D) All of the above E) None of the above

E) None of the above

When you state a two-tailed test for an experimental treatment that aims to change behavior, what does the appropriate alternative hypothesis state? A. The experimental treatment has no effect on the behavior B. The experimental treatment increased the behavior C. The experimental treatment decreased the behavior D. Both (a) and (b) are included in the two-tailed alternative hypothesis E. Both (b) and (c) are included in the two-tailed alternative hypothesis

E. Both (b) and (c) are included in the two-tailed alternative hypothesis

Using which of the following criteria of significance is most likely to lead to a Type I error? A) .10 B) .05 C) .01 D) .001

A) .10

If we retain the null hypothesis about the difference between two population means using the .05 criterion of significance, what is the probability that we have made a Type I error? A) 0 B) .05 C) .95 D) Cannot be determined from the information given

A) 0

A sample of N = 100 has a mean of 42.9. The population standard deviation is known to be 7.5. Which of the following null-hypothesized values of the population mean should be rejected using the .05 criterion of significance? A) 41.1 B) 42.2 C) 44.1 D) All of the above E) None of the above

A) 41.1

An assumption behind the use of a one-sample t test is that A. the population is normally distributed. B. the sample is normally distributed. C. the population variance is normally distributed. D. the population variance is known.

A. the population is normally distributed.

In one-sample t tests, we A. compare one sample mean with another. B. compare one sample mean against a population mean. C. compare two sample means with each other. D. compare a set of population means.

B. compare one sample mean against a population mean.

The importance of the underlying assumption of normality behind a one-sample means test A. depends on how fussy you are. B. depends on the sample size. C. depends on whether you are solving for t or z. D. doesn't depend on anything.

B. depends on the sample size.

The reason why we need to solve for t instead of z in some situations relates to A. the sampling distribution of the mean. B. the sampling distribution of the sample size. C. the sampling distribution of the variance. D. the size of our sample mean.

C. the sampling distribution of the variance.

If we retain the null hypothesis about the difference between two population means using the .05 criterion of significance, what is the probability that we have made a Type II error? A) 0 B) .05 C) .95 D) Cannot be determined from the information given

D) Cannot be determined from the information given

What is a Type II error? E. Incorrectly translating theory into hypotheses F. Failing to accept the alternative hypothesis when it is true G. Using an inappropriate test statistic for the hypotheses stated H. Rejecting the null hypothesis when it is true

F. Failing to accept the alternative hypothesis when it is true

I or II: A diet pill is approved by the FDA even though it isn't actually effective.

Type I Error

I or II: A girl breaks up with her boyfriend because "he cheated," but he's actually innocent.

Type I Error

I or II: A freshman is allowed into a bar, even though she is only 18 years old.

Type II Error

I or II: A graduate school candidate's application is misplaced, and therefore a professor overlooks the perfect candidate for his doctoral program.

Type II Error

I or II: A pregnancy test gives a negative result, even though the woman is in fact pregnant.

Type II Error