Quiz (Chapter 15)
The Analysis of Covariance
- The analysis of covariance is often referred to by means of what
- (T/F) The analysis of covariance can't be used in studies involving
factors that are within-subjects in nature.
- There ___ (is/isn't) an ANCOVA counterpart to any ANOVA.
The Three Different Variables Involved in Any ANCOVA Study
- ANCOVA studies contain at least one _____ variable in addition to
the independent and dependent variables.
- The variable identified in question 4 is more similar to the study's
_____ (independent/dependent) variable.
- The covariate variable is sometimes referred to as the _____ variable.
The Covariate's Role
- If a good covariate is used, the ANCOVA will have ___ (more/less)
power than will its ANOVA counterpart.
- A good covariate functions to ____ (increase/reduce) the size of
- While one function of the covariate is connected to "power," the
other function is related to "_____."
- In Excerpt 15.4, the "control" function of the ANCOVA functioned
to make the 2 sections comparable in terms of _______ (absence frequency/GPA).
- Will the group with the highest covariate mean have its mean on the
dependent variable adjusted up or down?
- (T/F) Researchers must choose to use a covariate either to increase
power or to use it to exercise control.
- How many null hypotheses were associated with the ANCOVAs in Excerpts
15.1? What about Excerpt 15.2?
- The ANCOVA null hypothesis always deal with adjusted ____ (sample/population)
means on which variable?
The Focus, Number, and Quality of the Covariate Variable(s)
- In ANCOVA studies, the covariate variable ___ (can/can't) be different
from the dependent variable.
- (T/F) Excerpt 15.5 is typical of ANCOVA studies in that only one
covariate variable was involved (rather than multiple covariate variables).
- The covariate variable ____ (should be/need not be) conceptually
related to the dependent variable.
Presentation of Results
- If a summary table is built to show the results of Excerpt 15.3's
ANCOVA, how many F-values would it contain?
- In Excerpt 15.7, the 2nd df associated with the 3rd F-ratio
is ______ (correct/incorrect)?
- Suppose ANCOVA is used in a study on thin people to compare two
different diets (A and B) on weight gain over a 4-week period. Suppose
further that pre-diet weight is the covariate while post-diet weight
is the dependent variable. Finally, suppose that the pre and post means
(in pounds) for people in diet A are 140 and 160, respectively, while
the pre and post means for people in diet B are 135 and 150. In this
study, ANCOVA would cause diet A's adjusted mean to be ____ (higher/lower)
than its unadjusted mean.
- In Excerpt 15.13, the mean scores contained in the excerpt's middle
sentence are _____ (cell/main effect) means.
The Statistical Basis for ANCOVAšs Power Advantage and Adjustment Feature
- In ANCOVA studies, a covariate variable will do a better job of increasing
power and providing control if it has a strong relationship with the
_____ (independent/dependent) variable.
- (T/F) In evaluating the relationship alluded to in Question 22, the
researcher should focus on the pooled within-group correlation rather
than the correlation based on all comparison groups thrown together.
- When multiple covariate variables are involved in an ANCOVA study,
those covariate variables work best if they have a _____ (strong/weak)
relationship with one another.
- The regular assumptions of ANOVA ___ (do/don't) apply to ANCOVA studies.
- One unique-to-ANCOVA assumption says that the _____ variable should
not affect the _____ variable.
- The assumption mentioned in Question 26 was ____ (met/violated)
in Excerpt 15.12.
- (T/F) With equal sample sizes, ANCOVA is robust to the assumption
of equal regression slopes.
- (T/F) If the sample sizes are equal, ANCOVA is robust to the assumption
- You are likely to come across ___ (many/few) ANCOVA studies in which
assumptions are not discussed.
ANCOVA When Comparison Groups Are Not Formed Randomly
- Are the comparison groups in Excerpt 15.9 "intact groups"? What
about the groups in Excerpt 15.20?
- When the population means on the covariate differ, ANCOVA's sample-based
adjusted means on the dependent variable ____ (will/won't) be biased.
- Simply on logical grounds, ANCOVA _____ (should/shouldn't) be viewed
as able to equate intact groups.
- The Bonferroni adjustment technique ___ (can/can't) be used in ANCOVA
- In Excerpt 15.20, d was used as an estimate of effect size.
Based on the criteria for evaluating this measure of practical significance,
the final of the 3 findings
would be labeled as being
- (T/F) With ANCOVA, only omnibus F-tests and post hoc comparisons
are possible, not planned comparisons.
A Few Warnings
- Your critique of an ANCOVA article should go ____ (up/down) if it
doesn't contain adjusted means.
- In testing assumptions, researchers should use an alpha level that's
more _____ (lenient/rigorous) than .05.
- Which of these studies would yield results that are easier to interpret:
(a) a one-way ANCOVA used with intact groups or (b) a one-way ANOVA
used with randomly formed groups?
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