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ANOVA TABLES

Fill in the missing values in each of the ANOVA tables below. (Gray cells should not contain values) 1.

SOURCE Between Within total

2.

SS 200 400

df 4 40

MS

F

SOURCE Between Within total

SS 12 68

df 3 14

MS

F

3. A pharmaceutical company has developed a drug that is expected to reduce hunger. To test the drug, three samples of rates are selected with n = 10 in each sample. The first sample receives the drug every day. The second sample is given the drug once a week, and the third sample receives no drug at all. The dependent variable is the amount of food eaten by each rat over a 1-month period. This is the ANOVA table for the study. Fill in the missing values.

SOURCE Between Within total

SS 54

df

MS

F 12

4. The following summary table presents the results of an ANOVA from an experiment comparing four treatment conditions with a sample of n = 10 in each treatment. Complete the table.

SOURCE Between Within total

SS 108

df

MS 15

F

5. A common science-fair project involves testing the effects of music on the growth of plants. For one of these projects, a sample of 24 newly sprouted bean plants is obtained. These plants are randomly assigned to four treatment conditions, with n = 6 in each group. The four conditions are rock, heavy metal, country, classical. The dependent variable is the height of the plant after 2 weeks. Fill in the missing values for the ANOVA table.

SOURCE Between Within total

SS 40

df

MS 10

F

TWO-FACTOR ANOVAs: MAIN EFFECTS & INTERACTIONS

Factor A ­ Sex (male, female) Factor B ­ Drug Dosage (none, small, large) no drug male female mean = 2 4 3 small dose 7 1 4 large dose 3 1 2 4 2 grand mean = 3

1.

In P x Q terms, what is the design of this study?

2.

In terms of the group means, what would it mean if there was a significant effect of A?

3.

In terms of the group means, what would it mean if there was a significant effect of B?

4.

If there was found to be a significant effect of A & B, would you need to do any post hoc analyses? Why or why not?

5.

If we assume that any difference in means is significant, does there appear to be an effect of sex? If so, explicate.

6.

Again assuming any difference in means is significant, does there appear to be an effect of drug dosage? If so, explicate.

7.

Again assuming any difference in means is significant, does there appear an interaction? If so, explicate it.

FILL-INS/MULTIPLE-CHOICE/SHORT ANSWER

1.

A one-way ANOVA differs from a two-way in the number of ___________.

2.

If I have a study with one IV and a DV, under what circumstances would I use an ANOVA and under what circumstances would I use a t-test?

3.

In a 2 x 3 ANOVA, how many ... factors are there? levels are there of each IV? cells are there (in a complete factorial design?

4. 5. 6. 7. 8.

If there is no effect of a factor, the corresponding F-statistic should take on what value? _______ As the F-statistic gets larger, p-values get ____________. SS-within could also be called SS-____________. In a one-way the SS for the factor is usually called SS-____________. One reason for using an ANOVA rather than a t-test when comparing 3 groups is that if you were to do multiple t-tests to test for differences among the groups, the experiment -wise error rate would a. increase b. decrease (circle one)

9.

You will all be doing a 2 x 2 ANOVA for your projects. Will you be needing to do a post-hoc analysis? Why or why not?

10. Use of the LSD post-hoc test was discouraged because ...

11. What is an omnibus test?

12. If a study ends up with a significant interaction, in explicating the results you want to emphasize or (main effects simple effects); if there is not an interaction, you would emphasize (main effects effects).

or

simple

13. If I find that the effect of factor A is true only at one level of factor B, this would be an example of a _________________ ________________.

EXAMPLE ANOVA 1

Use the SPSS output labeled "Example 1" to answer the questions below.

1.

What are the two IVs and what are the levels of each?

2. 3.

What is the DV? Fill in the means in each of the boxes from the SPSS printout

Note-taking method

Method 1 Method 2 Control

Gender

Men Women

4.

What 3 hypotheses are being tested?

5.

Was there a significant main effect of gender? If so, explain and make sure to give evidence of it (i.e., F, p-values, etc.).

6.

Was there a significant interaction? If so, explain.

7.

Overall, the mean for method 2 was significantly better than for method 1. However, the presence of an interaction complicates this so that this effect must be qualified. Explain this more fully.

8.

If someone asked you to summarize the results of the study, what could you tell them about the relationship between note-taking methods, gender, and GPA-improvements? Be sure to back up your statements with evidence.

EXAMPLE ANOVA 2

Use the SPSS output labeled "Example 2" to answer the questions below.

1.

What are the two IVs and what are the levels of each?

2.

What is the DV?

3.

Fill in the means in each of the boxes from the SPSS printout

Disability status of the child

Typically developing Physical disability Mental retardation

Gender

Male Female

4.

What 3 hypotheses are being tested?

5.

Was there a significant main effect of gender? If so, explain and make sure to give evidence of it (i.e., F, p-values, etc.).

6.

Was there a significant main effect of disability status? If so, explain.

7.

Was there a significant interaction? If so, explain.

8.

If someone asked you to summarize the results of the study, what would you tell them about the relationship between disability status, gender, and level of play complexity? Be sure to back up your statements with evidence.

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