Quiz (Chapter 12)


Post Hoc and Planned Comparisons

Introduction

  1. (T/F) With 3 comparison groups, Ho, if false, might be false because m1 = m2 while m3 is equal to something else.
  2. (T/F) Researchers use planned comparisons more often than they do post hoc comparisons.

Post Hoc Comparisons: Definition and Purpose
  1. (T/F) There is confusion among researchers as to what is or is not a post hoc test.
  2. What's the statistical focus of a post hoc test that's conducted in connection with a one-way ANOVA?
  3. (T/F) Post hoc tests are used when the Ho of a one-way analysis of variance is not rejected.

Post Hoc Comparisons: Terminology
  1. A post hoc test is sometimes referred to as a ______ test or a ______ test or an ______ test.
  2. Within the post hoc tests, what's a one-word synonym for "comparison"?
  3. (T/F) The F that comes from a one-way ANOVA can be referred to as the "omnibus F-test."
  4. If all possible "pairwise" comparisons had been conducted in Excerpt 11.9 (Chapter 11, p. 268), how many comparisons would have been made?
  5. Suppose we have 3 groups: undergrads, grad students in an M.S. program, & grad students in a Ph.D. program.  If the 2 groups of grad students are combined and compared against the undergrads, this is a _____ comparison.

Post Hoc Comparisons: Test Procedures Frequently Used
  1. Who invented the multiple comparison test that goes by the name "HSD"?
  2. Who invented the multiple comparison test that's called the "New Multiple Range Test"?
  3. Which of the 5 tests used most often to do post hoc comparisons is most "liberal"?  Most "conservative"?
  4. Which of these tests--Duncan, Tukey, Newman-Keuls-- protects most against Type I errors?  Type II errors?
  5. What is the name of the multiple comparison test that compares experimental groups versus the control group (but doesn't compare experimental groups against each other)?

Post Hoc Comparisons: The Null Hypothesis
  1. (T/F) A separate Ho exists for every comparison that's set up in a post hoc investigation.
  2. In Excerpt 12.18, there were __ post hoc null hypotheses.

Post Hoc Comparisons: Presentation of Results
  1. (T/F) Pairwise comparisons can be accomplished via Tukey's HSD procedure . . . but cannot be accomplished by the Tukey a or Tukey B procedures.
  2. In Excerpt 12.14, how many Tukey tests are being summarized?
  3. Suppose a Tukey test is used to make all pairwise comparisons among 4 means. Suppose further that these tests indicate that (a) the largest mean is signifficantly larger than the second-largest mean, (b) each of those means is significantly different from the other 2 means, and (c) the 2 smallest means are not significantly different from each other. If the "reporting scheme" used in Table 4 of Excerpt 12.18 is used to summarize these results, how many different letters would appear next to the sample means?
  4. If we let "1" represent the young group, "2" represent the middle group, and "3" represent the older group, which of the following statements accurately summarizes the results of the post hoc comparisons made in the last sentence of Excerpt 12.14?
  5. (a) 3<1<2, (b) 1<2<3, (c) 3<2=1, (d) 2<1<3, (e) 1=3<2

Post Hoc Comparisons: The Bonferroni Procedure as a Post Hoc Technique
  1. What a would be needed if the Bonferroni technique were to be used by a ".05" researcher who wants to conduct a post hoc analysis wherein all possible pairwise comparisons are made among 5 groups?

Planned Comparisons
  1. (T/F) Planned comparisons are turned to by the researcher if the ANOVA F turns out p > .05.
  2. (T/F) Since test procedures such as Tukey's were invented for use as post hoc investigations, they can't be used in situations where the researcher wants to conduct planned comparisons.
  3. A planned contrast is sometimes referred to as a ________ contrast.
  4. Return to question #2 and answer it again with these two changes: (a) insert the words "ought to" after the word "Researchers" and (b) delete the final 3 words of the sentence.
  5. (T/F) The planned comparisons set up by most researchers are nonpairwise (rather than pairwise) in nature.
  6. (T/F) In any given study having three or more comparison groups, the researcher can set up some planned comparisons that are nonpairwise in nature along with other planned comparisons that are pairwise in nature?

Comments
  1. If a planned comparison is set up to contrast one group's mean against the average of two other groups (that have been lumped together), what will the F-test's first df number be?
  2. (T/F) The term "orthogonal" means "independent."
  3. (T/F) The equal variance assumption is important when a researcher conducts an omnibus F-test but it is not important if he/she performs a planned or post hoc investigation.
  4. If three samples have means of 12.15, 18.50, and 21.75, the index d would turn out to be smallest for a comparison of which 2 means?
  5. (T/F) All of the test procedures developed for doing post hoc and planned comparisons have a built-in "control mechanism" that prevents the results from being statistically significant if there's no practical significance.
  6. Look again at Excerpt 12.26. The values of d can be thought of as "large" because they are larger than ___ .


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