Statistics Chapter 9

State the critical value(s) for a t test using a two-tailed test at a .05 level of significance: t(20). ±1.725 ±2.093 ±2.086 ±0.687

±2.086

Is a one-sample t test reported differently for one-tailed and two-tailed tests? No, the same values are reported. It depends on whether the results were significant. Yes, only significant results for a two-tailed test are reported. It can be reported differently when the effect size is large.

No, the same values are reported.

Two researchers (A and B) compute a two-independent sample t test. For both tests, the standard error is the same, but the mean difference between the groups is larger for Researcher A. Which test is more likely to result in a decision to reject the null hypothesis? Researcher A. Researcher B. The likelihood is the same for both researchers. There is not enough information to answer this question.

Researcher A.

Which of the following summarizes a t test that was significant and associated with a large effect size? t(22) = 3.02, p < .05, d = .36 t(30) = 1.03, p > .05, d = .20 t(60) = 1.76, p > .05, d = .45 t(12) = 2.95, p < .05, d = .82

t(12) = 2.95, p < .05, d = .82

Eta-squared is computed ______ for the one-sample, and the two-independent sample t tests. Differently Infinitely Similarly Semantically

Similarly

A researcher reports that the mean difference in response time to an auditory versus a visual cue is 0.83 seconds, with a pooled sample variance equal to 2.45. What is the effect size for this test using estimated Cohen's d? d = 0.53; medium effect size d = 0.53; large effect size d = 0.34; small effect size d = 0.34; medium effect size

d = 0.53; medium effect size

The more that scores in each group ________, the larger the error variance. do not overlap overlap are significant are dependent

overlap

Computing a two-independent sample t test is appropriate when different participants are assigned to each group the population variance is unknown participants are observed one time all of the above

all of the above

A research design in which different participants are observed one time in each group of a research study is within-subjects design between-subjects design mixed factorial design pre-post design

between-subjects design

A researcher reports that the effectiveness of a new marketing campaign significantly increased sales compared with the previous campaign strategy, t(49) = 2.562, p < .05. Use eta-squared to interpret the effect size for this result. 12% of the variability in marketing effectiveness can be accounted for by the new marketing strategy. 12% of the standard error can be accounted for by the effectiveness of the marketing strategy. Marketing effectiveness shifted 0.12 standard deviations above the mean in the population. both A and B are correct

12% of the variability in marketing effectiveness can be accounted for by the new marketing strategy.

A researcher reports that the mean difference in the body weight of rats following a pharmacological versus control treatment is 14 grams, with a pooled sample variance equal to 256. What is the effect size for this test using estimated Cohen's d? d = 0.06; small effect size d = 0.08; small effect size d = 0.88; large effect size There is not enough information to answer this question.

d = 0.88; large effect size

A researcher reports a significant mean difference in a given population. If she computes both eta-squared and omega-squared to measure the effect size, then which estimate will be the most conservative? eta-squared omega-squared It depends on the sample size. It depends on the value of the t statistic.

omega-squared

The less that scores overlap between groups, the ________ the error variance. larger more valuable smaller more sizable

smaller

To compute a two-independent sample t test, a researcher has to know many values. Which of the following is NOT a value that the researcher must know to compute this test? the pooled sample variance the pooled population variance the sample size for both samples the sample mean for both samples

the pooled population variance

As a requirement for the t test, researchers compute any type of t test with samples selected from populations in which the population variance is known the population size is very large the population variance is unknown the population is the same size as the sample

the population variance is unknown

State the critical value(s) for the following two-tailed t test at a .05 level of significance: t(∞). ±1.645 ±1.96 the same as for a two-tailed z test at a .05 level of significance both B and C

both B and C

State the critical value(s) for a t test using a .05 level of significance in the lower tail only: t(24). ±1.711 -1.711 ±2.064 -2.064

-1.711

In a sample of 30 participants, a researcher estimates the 95% CI for a sample with a mean of M1-M2= 0.7 and an estimated standard error for the difference (SM1-M2) of 0.2. What is the confidence interval at this level of confidence? 95% CI 0.4, 1.0 95% CI 0.5, 0.9 95% CI 0.3, 1.1 There is not enough information to answer this question.

95% CI 0.3, 1.1

Which of the following is an assumption for the two-independent sample t test, but not the one-sample t test? Normality Random sampling Independence Equal variances

Equal variances

Two researchers (A and B) compute a two-independent sample t test. For both tests, the mean difference between the two groups is 10, but the standard error is smaller for Researcher A. Which test is more likely to result in a decision to reject the null hypothesis? Researcher A. Researcher B. The likelihood is the same for both researchers. There is not enough information to answer this question.

Researcher A.

A researcher selects a sample of 32 participants who are assigned to participate in a study with two groups. What are the degrees of freedom for this test? 32 30 31 There is not enough information to answer this question.

31

A researcher conducts two t tests. Test 1 is a one-tailed test with a smaller sample size at a .05 level of significance. Test 2 is a one-tailed test with a larger sample size at a .05 level of significance. What do you know about the critical values for each test? Test 1 is associated with smaller critical values. Test 2 is associated with smaller critical values. Each test is associated with the same critical values. It depends; there is not enough information to answer this question.

Test 2 is associated with smaller critical values.

A type of factor in which different participants are observed in each group, or at each level of the factor, is called: within-subjects factor repeated measures factor mixed factor between-subjects factor

between-subjects factor

Which type of error is used to compute the confidence interval for two independent samples selected from at least one population with an unknown variance? standard error estimated standard error estimated standard error for the difference estimated standard error for the difference scores

estimated standard error for the difference

A researcher compares differences in mean health scores between students at a two local high schools. Assuming that the population variance is unknown, what type of t test is appropriate for this study? one-sample t test two-independent sample t test There is not enough information to answer this question.

two-independent sample t test

A researcher conducts a study measuring differences in brain activity among rats placed on either a continuous or intermittent reward schedule. Assuming that the population variance in unknown, what t test is appropriate for this study? one-sample t test two-independent sample t test not enough information

two-independent sample t test

A researcher records differences in ratings of emotion among participants watching either a drama or a romance film. Assuming that the population variance is unknown, what type of t test is appropriate for this study? one-sample t test two-independent sample t test There is not enough information to answer this question.

two-independent sample t test

A researcher conducts two t tests. Test 1 is a two-tailed test with a smaller sample size at a .05 level of significance. Test 2 is a two-tailed test with a larger sample size at a .05 level of significance. What do you know about the degrees of freedom for each test? Test 1 is associated with larger degrees of freedom. Test 2 is associated with larger degrees of freedom. Each test is associated with the same degrees of freedom. It depends; there is not enough information to answer this question.

Test 2 is associated with larger degrees of freedom.

A researcher reports that stress levels among nurses are higher compared to stress levels in the general population, t(20) = 2.086, p = .05 (d = .12). Was this a one-tailed or a two-tailed test? One-tailed test because the p value is equal to .05 Two-tailed test because the p value is equal to .05 It could be a one- or a two-tailed test

Two-tailed test because the p value is equal to .05

Which of the following is an assumption for computing any type of independent sample t test? Data in the population being sampled are normally distributed. Data were obtained from a sample that was selected using a random sampling procedure. The probabilities of each measured outcome in a study are independent. all of the above

all of the above