Stats Chapter 9
State the critical value(s) for a t test using a .05 level of significance in the lower tail only: t(24).
-1.711
A type of factor in which different participants are observed in each group, or at each level of the factor, is called:
between-subjects factor
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
The less that scores overlap between groups, the ________ the error variance
smaller
State the critical value(s) for a t test using a two-tailed test at a .05 level of significance: t(20).
±2.086
Is a one-sample t test reported differently for one-tailed and two-tailed tests?
No, the same values are reported
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
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?
30
A research design in which different participants are observed one time in each group of a research study is called:
between-subjects design
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 = 0.88; 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?
omega-squared
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 population variance
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?
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?
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?
two-independent sample t test
Which of the following is an assumption for the two-independent sample t test, but not the one-sample t test?
equal variances
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?
estimated standard error for the difference
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.
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 0.3, 1.1
Which of the following is an assumption for computing any type of independent sample t test?
All of the above (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.)
Computing a two-independent sample t test is appropriate when
All of the above (different participants are assigned to each group; the population variance is unknown; participants are observed one time)
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
Eta-squared is computed ______ for the one-sample, and the two-independent sample t tests.
Similarly
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 2 is associated with larger degrees of freedom
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 2 is associated with smaller critical values.
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?
Two-tailed test because the p value is equal to .05
The more that scores in each group ________, the larger the error variance.
overlap
Which of the following summarizes a t test that was significant and associated with a large effect size?
t(12) = 2.95, p < .05, d = .82
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 unkown
