exam three review

The F ratio is calculated by: a. dividing a measure of within-groups variability by a measure of between-groups variability. b. averaging the results from the t tests for all possible two-group comparisons. c. dividing a measure of between-groups variability by a measure of within-groups variability. d. squaring all the scores.

C. dividing a measure of between-groups variability by a measure of within-groups variability.

T or F As the number of t tests increases, the risk of a Type I error decreases.

F

T or F A significant main effect found in a two-way between-groups ANOVA trumps any significant interaction.

False

T or F A two-way between-groups ANOVA has just two hypotheses.

False

T or F Populations that have the same variance are referred to as homoscedastic.

True

T or F When the null hypothesis is true, the F ratio for analysis of variance is expected, on average, to be 1.

True

True or False Correlation involves relating variables, whereas regression involves prediction.

True

The owners of the Syfy channel are interested in whether watching the Syfy channel causes people to become "geeky," and if so, whether any such effects depend on a person's gender. They hire a researcher to design and carry out the appropriate study. The researcher randomly assigns an equal number of men and women to watch 0, 3, 5, or 9 hours of the Syfy channel each week for 6 weeks. How should the ANOVA used to analyze the data be labeled? a. 4 × 2 between-groups ANOVA b. 4 × 2 within-groups ANOVA c. 2 × 2 between-groups ANOVA d. 2 × 2 within-groups ANOVA

a. 4 × 2 between-groups ANOVA

With two groups, the square root of F is equal to: a. t. b. 0.0. c. 1.0. d. 2t.

a. t.

According to Cohen's conventions, an R2 of 0.07 is considered to be a(n) _____ effect size. a. small b. medium c. large d. erroneous

b medium

The numerical value for a correlation coefficient ranges between _____ and _____. a. 0; 1.00 b. -1.00; 1.00 c. -1.00; 0 d. negative infinity; positive infinity

b -1.00; 1.00

The Bonferroni, Scheffé, and Tukey are all examples of: a. hypothesis tests. b. post hoc tests. c. effect size statistics. d. a priori tests.

b; post hoc tests.

Within-groups designs reduce error due to differences between the groups by using the same participants in each group. If differences are then observed between the groups, those differences are attributed to: a. extraneous variables. b. differences between participants. c. failure to control other important variables. d. the manipulation of the independent variable.

d the manipulation of the independent variable.

The _____ sum of squares is unique to the within-subjects design. a. between-groups b. within-groups c. total d. subjects

d. subjects

T or F A factor is another word to describe the dependent variable in a two-way ANOVA.

false

T or F If two variables are negatively correlated, then low scores on one variable would be associated with low scores on the other variable.

false

True or false The intercept is the predicted value for X when Y is equal to 0.

false

The relation between a hockey player's age and the number of minutes he spent in the penalty box during the regular 2006-2007 season is shown in the figure. The 18 players, members of the New Jersey Devils hockey team, played in more than 40 games that season. Based on the scatterplot, what is the relation between a hockey player's age and the number of minutes he spent in the penalty box? a. perfect positive b. positive c. negative d. no relation

negative

T or F Post hoc tests are frequently carried out after the null hypothesis has been rejected in an ANOVA.

true

hmm

yes

The following figure reflects the results of a study by Roediger and Karpicke (2006). The authors investigated whether the test-enhanced learning effect (the demonstration that repeated testing improves memory for material) was due merely to repeated exposure to the material. They randomly assigned participants to one of two study conditions (study-study or study-test) and to one of three retention interval conditions (final test at a delay of 5 minutes, 2 days, or 1 week). The dependent variable was the proportion of idea units recalled from an encyclopedia passage.

a. On average, people in the study-test condition had better memory than people in the study-study condition.

A researcher wants to statistically test whether gender affects math test scores. Which type of ANOVA design should the researcher use? a. between-groups b. within-groups c. mixed-groups d. repeated-measures

a. between-groups

True or False If two variables are negatively correlated, they cannot be causally related.

False

True or false Correlation coefficients at or near 0.00 are considered perfect correlations.

False

True or false Simple linear regression is a statistical technique that includes two or more predictor variables in a prediction equation.

False

Determine the critical cutoff for F at a p level of 0.05 if the following degrees of freedom were calculated for a one-way within-groups ANOVA: dfbetween = 4, dfsubjects = 5, dftotal = 29, dfwithin = 20. a. 2.71 b. 2.87 c. 2.70 d. 5.19

b 2.87

Which of these is NOT an assumption of an ANOVA? a. random selection b. independent variable has only three levels c. normally distributed population d. samples come from populations with the same variances

b independent variable has only three levels

The F statistic increases when: a. within-groups variance decreases. b. between-groups variance decreases. c. between-groups variance increases. d. within-groups variance decreases and between-groups variance increases.

b within-groups variance decreases and between-groups variance increases.

In which situation would it NOT be appropriate to use a one-way ANOVA? a. A researcher is interested in a longitudinal study that follows a group of kindergarten children through high school; he assesses their body mass index at four time points. b. A researcher classifies a group of college students on the basis of their political leanings as liberal, conservative, libertarian, or green. c. A researcher interested in the effects of distraction on driving performance randomly assigns participants to one of three distraction groups. d. A researcher is interested in whether a sensitivity training class changes attitudes toward minority populations. The researcher assesses these attitudes before, immediately after, and 6 months after the sensitivity training class. b. A researcher classifies a group of college students on the basis of their political leanings as liberal, conservative, libertarian, or green.

b. A researcher classifies a group of college students on the basis of their political leanings as liberal, conservative, libertarian, or green.

The figure reflects an interaction. Which statement best describes the interaction? a. On average, people in the study-test condition had better memory than people in the study-study condition. b. People in the study-test condition performed more poorly on the 5-minute recall test than did those in the study-study condition, but at longer retention intervals (2 days and 1 week); those in the study-test condition performed better than those in the study-study condition. c. On average, memory performance decreased as the retention interval increased. d. On average, memory performance increased as the retention interval increased.

b. People in the study-test condition performed more poorly on the 5-minute recall test than did those in the study-study condition, but at longer retention intervals (2 days and 1 week); those in the study-test condition performed better than those in the study-study condition.

Buying jeans can be a challenge for women. A local shop owner wants to be selective in what brands of jeans she carries in her store. She gets six of her closest friends to try five different pairs of jeans, with the requirement that they wear each pair for two whole days, without washing, and they rate the jeans at the end of the second day. What research design should she use to analyze her data? a. one-way between-groups ANOVA b. independent-samples t tests c. one-way within-groups ANOVA d. paired-samples t tests

c one-way within-groups ANOVA

What kind of correlation would one expect to find between the severity of snowstorms and rates of attendance at college classes? a. positive b. zero c. negative d. perfect negative

c negative

An F statistic calculated on 2 and 26 degrees of freedom equals 3.41. Which decision should be made about a hypothesis tested at the p = 0.05 level? a. Fail to reject the null hypothesis and conclude that there are differences among the groups. b. Fail to reject the null hypothesis and conclude that no significant differences are indicated among the groups. c. Reject the null hypothesis and conclude that there are differences among the groups. d. Reject the null hypothesis and conclude that no significant differences are indicated among the groups.

c. Reject the null hypothesis and conclude that there are differences among the groups.

What is(are) the main effect(s) being tested in the study for the previous question? a. gender b. hours of Syfy watched c. gender and hours of Syfy watched d. hours of Syfy watched and "geekiness"

c. gender and hours of Syfy watched

In addition to assessing whether each independent variable has an effect on the dependent variable, a factorial ANOVA also allows one to: a. use multiple dependent measures in a single analysis. b. control for a third variable that might be related to the dependent measure, prior to investigating the independent variable of interest. c. determine whether the effects of one factor depend on the other factor. d. partition out the variability due to individual differences and the variability due to measurement error.

c. Determine whether the effects of one factor depend on the other factor.

The figure reflects an interaction. Is this interaction a quantitative or qualitative interaction? Why? a. The figure reflects a quantitative interaction; the effect of study condition does not reverse depending on the retention interval. b. The figure reflects a qualitative interaction; the effect of study condition does not reverse depending on the retention interval. c. The figure reflects a quantitative interaction; the effect of study condition reverses depending on the retention interval. With the 5-minute retention interval, study-study is better than study-test, but with longer retention intervals, study-test is better than study-study. d. The figure reflects a qualitative interaction; the effect of study condition reverses depending on the retention interval. With the 5-minute retention interval, study-study is better than study-test, but with longer retention intervals, study-test is better than study-study.

d. The figure reflects a qualitative interaction; the effect of study condition reverses depending on the retention interval. With the 5-minute retention interval, study-study is better than study-test, but with longer retention intervals, study-test is better than study-study.

Based on the data presented in the figure, which effects appear to be present? a. a main effect of study condition and an interaction between study condition and retention interval b. an interaction between study condition and retention interval c. a main effect of study condition and a main effect of retention interval d. a main effect of study condition, a main effect of retention interval, and an interaction between study condition and retention interval

d. a main effect of study condition, a main effect of retention interval, and an interaction between study condition and retention interval