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 ANOVA adjusted
the MET and SC means of the _____ (baseline/post-treatment) level of smoking .
- 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?
- If a summary table is built for Excerpt 15.7's ANCOVA, how many
Total df would there be?
- 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 15.14, the post hoc investigation focused on _____ (cell/main effrect)
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 2 groups in Excerpt 15.8 "intact groups"? What about the
2 groups in Excerpt 15.15?
- 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 15.13, two values of eta squared are provided. Based
on the criteria for evaluating these indices, the size of the significant
Treatment effect (when the dependent variable was "solitary play") would be
classified 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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