ch 9,10, & 12

State whether each of the following related samples t-tests is significant for a two-tailed test at a 0.05 level of significance. t(12) = 2.049 a. Yes, the test is significant. b. No, the test is not significant.

b

A researcher compares differences in positivity between participants in a low-, middle-, or upper-middle-class family. If she observes 15 participants in each group, then what are the degrees of freedom for the one-way between-subjects ANOVA? a. (2, 12) b. (3, 43) c. (2, 42) d. (3, 12)

c

T/F A t distribution with infinite degrees of freedom is a z distribution.

true

Using Cohen's d, state whether a 3-point treatment effect (M1 − M2 = 3) is small, medium, or large for a two-independent sample t-test sp^2 = 441 a. small b. medium c. large

a

Using Cohen's d, state whether a 3-point treatment effect (M1 − M2 = 3) is small, medium, or large for a two-independent sample t-test sp^2 = 144 a. small b. medium c. large

b

A professor compares scores on a competency exam among students at two times during a single semester. What type of t test is most appropriate for this study? a. one-sample t test b. two-independent sample t test c. related samples t test d. There is not enough information to answer this question.

c

T/F A researcher must know the population variance in order to compute a t test.

false

Computing a one-sample t test is appropriate when a. participants are assigned to only one group b. the population variance is unknown c. participants are observed one time d. all of the above

d

A researcher conducts a one-way ANOVA in which one independent variable has four levels. How many different groups are in this study?

4

A researcher measures mean health scores of children at a local school and compares these scores to the mean health score known in the general population. Assuming that the population variance is unknown, what type of t test is appropriate for this study? a. one-sample t test b. two-independent sample t test c. There is not enough information to answer this question.

a

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? a. d = 0.53; medium effect size b. d = 0.53; large effect size c. d = 0.34; small effect size d. d = 0.34; medium effect size

a

State whether each of the following related samples t-tests is significant for a two-tailed test at a 0.05 level of significance. t(30) = 3.470 a. Yes, the test is significant. b. No, the test is not significant.

a

tests is significant for a two-tailed test at a 0.05 level of significance. t(60) = 1.963 a. Yes, the test is significant. b. No, the test is not significant.

b

A principal at a local school wants to know how much students gain from being in an honors class. He gives students in an honors English class a test prior to the school year and again at the end of the school year to measure how much students learned during the year. a. one-independent sample t-test b. two-independent sample t-test c. related samples t-test using the repeated measures design d. related samples t-test using the matched-pairs design

c

A researcher records the level of attention among 18 students during an interactive and lecture portion of a single class. If she computes a related samples t test at a 0.05 level of significance (two-tailed test), then what is the critical value for this test? a. ±1.734 b. ±1.740 c. ±2.110 d. ±2.101

c

Following a significant one-way between-subjects ANOVA in which k > 2, what is the next appropriate step? a. Summarize the data; no further tests are required. b. Interpret the data; no further tests are required. c. Conduct post hoc tests. d. Both summarize the data and interpret the data with no further tests required.

c

Using Cohen's d, state whether a 3-point treatment effect (M1 − M2 = 3) is small, medium, or large for a two-independent sample t-test sp^2 = 9 a. small b. medium c. large

c

What measure of effect size is most often reported with the t-test? a. eta-squared (η^2) b. omega-squared (ω^2) c. estimated Cohen's d

c

"Elementary school children spent significantly more time reading in the presence of a teacher than when the teacher was absent, t(7) = 2.804, p < 0.05 (ω2 = 0.46)." In this related samples t test, how many participants were observed? a. 5 b. 6 c. 7 d. 8

d

A researcher matched 30 participants on intelligence (hence 15 pairs of participants), and then compared differences in emotional responsiveness to two experimental stimuli between each pair. For this test, what are the critical values, assuming a two-tailed test at a 0.05 level of significance? a. ±2.042 b. ±2.045 c. ±2.131 d. ±2.145

d

In a study with three groups and 13 participants in each group, the sum of squares for the within-groups source of variation is 18. What is the value for the mean square within-groups in this study? a. 2 b. 3 c. 9 d. 0.5

d

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

d

T/F A one-way between-subjects ANOVA is conducted to test for mean differences between the levels of two or more factors.

false

A professor tests whether students sitting in the front row score higher than students sitting in the back row. a. one-independent sample t-test b. two-independent sample t-test c. related samples t-test using the repeated measures design d. related samples t-test using the matched-pairs design

b

What are the degrees of freedom for the related samples t test? a. (nD − 1) b. (n − 1) (n − 1) c. (n − 1) + (n − 1) d. (n − 1) − (n − 1)

a

You read about a study testing whether night shift workers sleep the recommended 8 hours per day. Assuming that the population variance of sleep (per day) is unknown, what type of t test is appropriate for this study? a. one-sample t test b. two-independent sample t test c. There is not enough information to answer this question.

a

A researcher reports that the mean time it takes to complete an experimental task is 1.4 ± 8.0 (M ± SD) seconds. If the null hypothesis was that the mean equals 1.0, then what is the effect size for this test using estimated Cohen's d? a. d = 0.05; small effect size b. d = 0.50; medium effect size c. d = 1.05; large effect size d. There is not enough information to answer this question.

a

A researcher asks a sample of brothers and sisters to rate how positive their family environment was during childhood. In this study, the differences in ratings between each brother and sister pair were compared. The type of design described here is called a a. repeated measures design b. matched samples design c. all of the above

b

A type of related samples design in which participants are observed more than once is called a a. repeated measures design b. matched pairs design c. matched samples design d. both matched pairs design and matched samples design

a

tests is significant for a two-tailed test at a 0.05 level of significance. t(18) = 2.458 a. Yes, the test is significant. b. No, the test is not significant.

a

A researcher matches right-handed and left-handed siblings to test whether right-handed siblings express greater emotional intelligence than left-handed siblings. a. one-independent sample t-test b. two-independent sample t-test c. related samples t-test using the repeated measures design d. related samples t-test using the matched-pairs design

d

A graduate student selects a sample of 25 participants to test whether the average time students attend to some task is greater than 30 minutes. a. one-independent sample t-test b. two-independent sample t-test c. related samples t-test using the repeated measures design d. related samples t-test using the matched-pairs design

a

The mean crying time of infants during naptime at a local preschool is 12 minutes. The school implements a new naptime routine in a sample of 25 infants and records an average crying time of 8 ± 4.6 (M ± SD) minutes. Test whether this new naptime routine reduced crying time at a 0.05 level of significance. a. The new naptime routine significantly reduced crying time, t(24) = −4.35, p < 0.05. b. The new naptime routine did not reduce crying time, t(24) = −4.35, p < 0.05. c. The new naptime routine did not reduce crying time, t(24) = 0.92, p > 0.05. d. The new naptime routine significantly reduce crying time, t(24) = 0.92, p < 0.05.

a

A researcher assigns 21 adolescents to rate the likability of a person described in a vignette as having one of three personality traits. An equal number of participants are assigned to each group. If Fobt = 4.08 for this study, then what was the decision at a 0.05 level of significance for a one-way between-subjects ANOVA? a. Reject the null hypothesis. b. Retain the null hypothesis. c. There is not enough information to answer this question.

a

A researcher computes the mean difference in locomotion in a sample of 12 rats before and 30 minutes after an injection of amphetamine. Rats were placed in a box with infrared beams. The number of times rats crossed the beams was used as a measure of locomotion. The mean difference in locomotion was 6.2 ± 8.4 (MD ± SD), and this difference was significant. What is the effect size for this result using estimated Cohen's d? a. d = 0.74 (medium effect) b. d = 1.36 (medium effect) c. d = 0.74 (large effect) d. d = 1.36 (large effect)

a

How does the shape of a t-distribution change as the sample size increases? Explain. a. As sample size increases, the sample variance more closely estimates the population variance. The result is that there is less variability in the tails of a t-distribution as the sample size increases—the tails approach the x-axis faster. b. As sample size increases, the sample variance becomes less like the population variance. The result is that there is more variability in the tails of a t-distribution as the sample size increases—the tails approach the x-axis more slowly. c. As sample size increases, the sample variance estimate of the population variance does not change. The result is that there is a constant amount of variability in the tails of a t-distribution as the sample size increases—the tails approach the x-axis at the same rate.

a

Two researchers (A and B) compute a one-sample t test. For both tests, the mean difference between the sample and value stated in the null hypothesis is 5, but the standard error is smaller for Researcher A. Which test is more likely to result in a decision to reject the null hypothesis? a. Researcher A. b. Researcher B. c. The likelihood is the same for both researchers. d. There is not enough information to answer this question.

a

A professor compared differences in class grades between students in their freshman, sophomore, junior, and senior years of college. If different participants were in each group, then what type of statistical design is appropriate for this study? a. a two-independent sample t test b. a one-way between-subjects ANOVA c. a two-way between-subjects ANOVA d. both a two-independent sample t test and a one-way between-subjects ANOVA

b

Are post hoc tests necessary following a significant ANOVA testing one independent variable with two levels (k = 2)? Explain. a. Yes. When a variable has only two levels, then those two levels must be checked to determine if they are significantly different following a significant ANOVA. A post hoc test is necessary. b. No. When a variable has only two levels, then those two levels must be significantly different following a significant ANOVA. There are no multiple comparisons to make, so a post hoc test is not necessary.

b

The following is a summary of a one-way between-subjects ANOVA: F(2, 37) = 3.42, p < 0.05, η2 = 0.12. How many pairwise comparisons need to be made for this ANOVA result? a. 2 b. 3 c. 4 d. 12

b

Using Cohen's d, state whether a 3-point treatment effect (M1 − M2 = 3) is small, medium, or large for a two-independent sample t-test sp^2 = 25 a. small b. medium c. large

b