hw 5
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? - (3, 43) - (2, 12) - (3, 12) - (2, 42)
(2, 42)
On average, what value is expected for the F-ratio if the null hypothesis is true? - 0 - k - 1 - N - k - 1.00
1.00
An analysis of variance produces SSbetween = 30, SSwithin = 60, and an F-ratio with df = 2 and 15. For this analysis, what is the F-ratio? - 30/60 = 0.50 - 15/4 = 3.75 - 60/30 = 2.00 - 4/15 = 0.27
15/4 = 3.75
An independent-samples study with n = 6 in each of the two samples, produces a sample mean difference of 4 points and a pooled variance of 12. What is the value for the t statistic? - 4/6 - 1 - 4/8 - 2
2
What is the pooled variance for the following two independent samples? Sample 1: n = 8 and SS = 168 Sample 2: n = 6 and SS = 120 - 20.57 - 7 - 27 - 24
24
A researcher computes a 2 × 4 between-subjects ANOVA. What are the degrees of freedom for Factor B for this study? - 8 - 2 - 3 - 4
3
In a sample of 28 participants, a researcher estimates the 95% CI for a sample with a mean of 1.5 and an estimated standard error of 0.3. What is the confidence interval at this level of confidence? - 95% CI (1.2, 1.8) - 95% CI (0.9, 2.1) - 95% CI (1.0, 2.0) - There is not enough information to answer this question.
95% CI (0.9, 2.1)
What is stated by the null hypothesis (H0) for an ANOVA? - There are no differences between any of the population means. - The estimate is significant. - At least one of the population means is different from another mean. - All of the population means are different from each other.
There are no differences between any of the population means.
The t distribution is similar to the z distribution except ______. - it is characterized by "thicker" tails compared with the z distribution - it is associated with greater variability - all of these - it is associated with scores being more likely in the tails of the distribution
all of these
The test statistic for a related-samples t test makes tests concerning a single sample of ______. - raw scores - participant scores - original data - difference scores
difference scores
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? - There is not enough information to answer this question. - two-independent-sample t test - related-samples t test - one-sample t test
related-samples t test
For an analysis of variance, the term "two-way" refers to ______. - the number of statistical tests in the design - the number of factors in the design - the number of ways that the data can be analyzed - the direction that traffic should follow on a road
the number of factors in the design
The source of variability associated with error variance in the one-way between-subjects ANOVA is called ______. - both between-groups and within-groups variability - between-groups variability - within-groups variability - degrees of freedom
within-groups variability
State the critical value(s) for a t test using a two-tailed test at a .05 level of significance: t(20). - ±2.093 - ±1.725 - ±2.086 - ±0.687
±2.086
An analysis of variance produces SSbetween = 40 and MSbetween = 20. In this analysis, how many groups are being compared? - 4 - 2 - 20 - 3
3
In a sample of 20 participants, a researcher estimates the 95% CI for a sample with a mean of 5.4 and an estimated standard error of 1.6. What is the upper confidence limit for this interval? - 3.8 - 8.8 - 2.1 - 7.0
8.8
A researcher conducts a related-sample study to evaluate two treatments with n = 16 participants and obtains a t statistic of t = 1.94. The treatment 2 is expected to have a greater sample mean than the treatment 1. What is the correct decision for a hypothesis test using α = .05? - Reject the null hypothesis with a one-tailed test but fail to reject with two tails. - Reject the null hypothesis with either a one-tailed or a two-tailed test. - Fail to reject the null hypothesis with either a one-tailed or a two-tailed test. - Fail to reject the null hypothesis with a one-tailed test but reject with two tails.
Reject the null hypothesis with a one-tailed test but fail to reject with two tails.
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? - It depends; there is not enough information to answer this question. - 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.
Test 2 is associated with larger degrees of freedom.
The mean crying time of infants during naptime at a local preschool is 12 mins. The school implements a new naptime routine in a sample of 25 infants and records an average crying time of 8 mins (SD=4.6). Test whether this new naptime routine reduced crying time at a .05 level of significance. - The new naptime routine did not reduce crying time, t(24) = -4.35, p < .05. - The new naptime routine significantly reduced crying time, t(24) = -4.35, p < .05. - The new naptime routine significantly reduced crying time, t(24) = 8.67, p < .05. - The new naptime routine did not reduce crying time, t(24) = 8.67, p > .05.
The new naptime routine significantly reduced crying time, t(24) = -4.35, p < .05.
When comparing more than two group means, should you use an analysis of variance rather than using several t tests, and if so, why? - Yes. Using several t tests increases the risk of a Type II error. - No. There is no advantage to using an analysis of variance rather than several t tests. - Yes. Using several t tests increases the risk of a Type I error. - Yes. The analysis of variance is more likely to detect a treatment effect
Yes. Using several t tests increases the risk of a Type I error.
