Exam 2 (8-14)
The assumption that the best way to describe a pattern of data is using a straight line is
linearity
There are ____ cells or groups in a 2 × 4 ANOVA design.
8
The ________ is an inferential statistic used to determine the number of standard deviations in a t distribution that a sample mean deviates from the mean value or mean difference stated in the null hypothesis.
t statistic
To compute the related samples t test, we assume independence within groups, and between groups.
False
The Spearman correlation coefficient is used to measure the correlation between two ordinal variables.
True
Which of the following indicates the strongest correlation?
r = -0.90
To report the results of a t-test, which of the following is not reported?
the critical values
The denominator of the correlation coefficient measures the extent to which two variables
vary independently
A researcher compares differences in response to shock among rats given an electric stimulation of 1, 3, and 5 volts. If she observes 20 rats in each group, then what are the degrees of freedom for the one-way between-subjects ANOVA?
(2, 57)
When the difference between two groups is compared, the pooled standard deviation is used as an estimate for the population standard deviation in the effect size formula for estimated Cohen's d.
True
A key difference between a t statistic and a z statistic is that the standard error is ________ to compute a t statistic.
estimated
The denominator of the test statistic for a related samples t test
estimated standard error for difference scores
The number of levels of the factor in a study is indicated by
k
A researcher reports the following result for a t-test at a .05 level of significance: t(40) = 3.02, p < .05 (d = .22). Is this result significant?
yes, for both a one- or a two-independent sample t-test
For an analysis of variance, the term "two-way" refers to
the number of factors in the design
A researcher computes a 3 × 3 between-subjects ANOVA in which 8 participants are observed in each cell. What are the degrees of freedom error for this study?
63
A one-way between-subjects ANOVA is conducted to test for mean differences between the levels of one factor.
True
If a study has 16 groups, then it is possible that the degrees of freedom for each factor are 3 and 3 for a two-way between-subjects ANOVA.
True
The mean square is the same as a variance since it is SS divided by the degrees of freedom.
True
The phi correlation coefficient is used to measure the correlation between two nominal variables.
True
A researcher computes the following test statistic for a one-independent sample t test, t(16) = 2.900, p < .05. What is the proportion of variance for this test using the formula for omega-squared?
.30
A researcher reported the following results for a one-way between-subjects ANOVA: F(1, 28)= 3.511. How many participants were observed in this study?
30
A researcher computes a 2 × 3 between-subjects ANOVA and graphs the cell means, with levels of Factor A on the x-axis and levels of Factor B on the Y-axis. The lines obtained are parallel, indicating
No significant interaction.
Computing a one-sample t test is appropriate when
all of the above
An ____________ is a measure of how cell means at each level of one factor change across the levels of a second factor
interaction
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 unknown
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 type of t test is appropriate for this study?
two-independent sample t test
A researcher measures the following correlation: r = -0.6. What is the value of the coefficient of determination?
0.36
The numerator of the test statistic for a related samples t test
the mean differences observed minus the mean difference stated in a null hypothesis
Covariance refers to the extent to which the values of two factors
vary together
Participants in a study for a new medicine reported significantly less pain 30 minutes after taking the pill than before taking the pill, t(9) = 3.804, p < .05 (w2 = 0.56)." In this related samples t test, how many participants were observed?
10
Which of the following is an assumption for the two-independent sample t test, but not the one-sample t test?
Equal variances
A researcher must know the population variance in order to compute a t test.
False
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.
The t-statistic is an inferential statistic used to determine the number of standard deviations in a t-distribution that a sample mean deviates from:
a mean value or mean difference stated in the null hypothesis
A _______________ is a statistical procedure used to describe the strength and direction of the linear relationship between two factors
correlation
A professor computes the mean difference in aggressive responses from participants before and after watching a video showing violence as 9.0±14.5 (MD +SD), and this difference was significant. What is the effect size for this result using estimated Cohen's d?
d = 0.62 (medium effect)
A researcher surveys the studying habits of students in his class, and then matches them based on this survey, so he could study the effectiveness of group work. This procedure is called
matching through experimental manipulation
One difference between a repeated measures design and a matched samples design is that
only one design involves observing the same participants in each group
A type of related samples design in which researchers measure a dependent variable for participants before and after a treatment is called a
pre-post design
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
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
The one-independent sample t-test can be computed only when:
the population being sampled from is normally distributed
Computing a one-way between-subjects ANOVA is not appropriate when
the same participants are observed in each of two or more groups for one factor
The most common measure of effect size for the correlation coefficient is called
the coefficient of determination
The complexity of the two-way ANOVA differs from that of the t tests and the one-way ANOVAs in that,
all of the above
All post hoc tests control for Type II error.
False
The coefficient of determination is the square of the correlation coefficient.
True
The repeated measures design, is associated with greater power to detect an effect compared with the independent samples design.
True
Observing different participants one time in each group is referred to as
between-subjects
The numerator of the correlation coefficient measures the extent to which two variables
both A and C
The related samples design decreases ____________ thereby increasing ________, compared to the two-independent samples design.
standard error; power
For a one-way between-subjects ANOVA, a study with 2 and 36 degrees of freedom, the degrees of freedom for the denominator is 38.
False
Homoscedasticity is the assumption that there is an unequal variance of data points dispersed along the regression line.
False
If d = 0.28, then we conclude that mean scores in some population have shifted 0.28 standard deviations below the mean.
False
R^2 is a more powerful estimate of effect size than Eta-squared.
False
The point-biserial correlation coefficient is used to measure the correlation between two continuous variables.
False
There are two factors and four cells in a 3 × 4 between-subjects ANOVA
False
When the variability attributed to between-groups is less than the variability attributed to error, then the value of the test statistic for a one-way between-subjects ANOVA is,
Not significant.
What value is placed in the denominator of the formula for estimated Cohen's d for the one-independent sample t test?
sample standard deviation
A researcher computes a two-independent sample t test and finds that the result is undefined (the denominator is equal to 0). This happens when there is no difference between the two groups (i.e., the mean difference is equal to 0).
False
Two research studies on the effectiveness of a training program revealed the following results: the sum of squares between groups was larger in Study 1 than in Study 2; the sum of squares total is smaller in Study 1 than in Study 2. Using eta-squared, in which study will the effect size be larger?
Study 1
Effect size measures are an estimate of the size of an effect in a population.
True
The test statistic for the related samples t test is not equivalent to the test statistic for the two-independent sample t test.
True
Unlike eta-squared, the formula for omega-squared corrects for the number of groups and the size of error in its estimate of effect size.
True
The degrees of freedom for the related samples t test is the total number of participants minus one, and not the total number of pairs minus one.
False
An estimated Cohen's d is interpreted in terms of the number of standard deviations that an effect shifted in some population.
True
An example of matching by natural occurrence would be if we matched participants based on their gender (male, female).
True
Early experiments in learning showed that rats learned a maze quickly when rewarded. A researcher records the time taken for rats to learn a route in the presence and absence of food. If the researcher tested the hypothesis that presence of food would produce faster learning, at a .05 level of significance (two-tailed test), then what is her decision if she computes t = 2.842 in a sample of 8 rats.
Reject the null hypothesis; there is evidence for faster learning.
A researcher conducts a one-independent sample t-test. What are the critical values for a two-tailed hypothesis test at a .05 level of significance when df = 14?
2.145
A two-independent sample t test is used when the same participants are observed in each of two groups.
False
The correlation coefficient ranges from -1.0 to +1.0, with values closer to ±0.0 indicating
that two factors are less likely to be related
Which of the following is a post hoc test for a one-way between-subjects ANOVA?
Tukey's HSD test
Participants in a study were assigned to groups based on their year in college (sophomore, junior, senior) and gender (male, female). What type of factorial design is most appropriate for this study?
a between-subjects factorial design
The estimated standard error in the t statistic uses the ________ to estimate the ________ when the population variance is unknown.
sample variance; population variance
A researcher groups college students in a study based on their year in college (junior, senior) and their major in college (engineering, arts, sciences). He concludes that perceptions of college life are more positive among seniors majoring in the arts. To reach this conclusion, which statistical test would need to be computed?
all of the above
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?
d = 0.05; small effect size
Why does the t-distribution have greater variability in the tails of the distribution compared to a normal distribution?
because the sample variance is substituted for the population variance to estimate the standard error in this distribution
Cohen's d is a measure of proportion of variance.
False
Is a one-sample t test reported differently for one-tailed and two-tailed tests?
No, the same values are reported.
A researcher computes the following one-way between-subjects ANOVA table. State the decision at a .05 level of significance. (Hint: Complete the table first.) Source of Variation SS df MS F Between groups 50 5 Within groups (error) 45 Total 140
Reject the null hypothesis.
Using the two-way mixed ANOVA, different participants are observed at each level of the between-subjects factor.
False
A researcher records the amount of time spent by male and female college students on a computer vs. playing a sport. Different participants were observed in each group. What type of statistical design is appropriate for this study?
two-way between-subjects ANOVA
Which measure of effect size is most commonly reported with a t test?
Cohen's d
Computing a two-independent sample t test is appropriate when
all of the above
All other things being equal, as the sample size decreases, what happens to the critical value for a related samples t test (or for any t test, for that matter)?
The critical value increases.
The factorial design is a research design in which participants are observed
across the combination of levels of two or more factors.
The correlation coefficient measures the extent to which changes in one factor are _______ in a second factor.
related to changes
Among the post hoc tests _________________ is too conservative when the number of pairwise comparisons is greater than three.
Bonferroni test
There are two sources of variation in a one-way between-subjects ANOVA: one attributed to differences between groups and one attributed to factor.
False
