Lecture 9

Question 1

Who invented ANOVA?

Answer 1

Sir Ronald Fisher (hence, F statistic)

Question 2

ANOVA can be used in a very wide range of experiment designs which are?

Answer 2

• independent groups
• treated measures
• matched samples
• designs involving mixtures of independent groups and repeated measures
• more than one independent variable can be evaluated at the same time

Question 3

What is the statistics used in ANOVA?

Answer 3

f statistic (the F ratio)

Question 4

The F statistic is a ratio formed as?

Answer 4

Between-group variability divides by within-group variability

AND

Treatment + individual differences + experimental error divided by individual differences + experimental error (error term)

Question 5

The _____ the treatment effect, the bigger the value of the __ ____.

Answer 5

Stronger; F ratio

Question 6

What are the most important details in ANOVA?

Answer 6

F ratio and the significance level (labelled p in SPSS)

Question 7

What does it mean if p value is less than .05?

Answer 7

You can conclude that there is a significant difference among your groups.

Question 8

What is the F test?

Answer 8

It tells you that there is a significant effect somewhere among your groups, but doesn’t tell you the source of the difference.

Question 9

What do you need to follow up in order to locate the source of the significant difference?

Answer 9

f test

Question 10

When do you carry out a post-hoc test?

Answer 10

This test is carried out after youbhave ovtained the significant overall ANOVA in order to locate the source of the significant F. exploratory, fishing expeditions.

Question 11

Overall F must be ______ in order to justify the use of ____ tests.

Answer 11

Significant; post-hoc

Question 12

There are different post- hoc tests. The one you choose depends on your research situation. Some common post-hoc tests?

Answer 12

• Scheffé test
• Newman- Keuls test
• Tukey’s Honestly Sifnificant Different test
• Fisher’s Least Significant Different Test

Question 13

What does a post- hoc test do?

Answer 13

Test every group with every other group

Question 14

What does pairwise comparisons ask?

Answer 14

Is there a significant difference between this pair of means?

Question 15

What is degrees of freedom?

Answer 15

Figures that the F test use to calculate its exact value.

Question 16

What are the two degrees of freedom for each F test?

Answer 16

1. Number of groups -1

2. (Number of subjects in each group-1) x number of groups

Question 17

What is established hypotheses?

Answer 17

Having some very clear, set ideas about what is going to happen.

Question 18

What is planned comparisons?

Answer 18

It’s a specific hypotheses test involving specific sub-groups of your experiment, and are carried out instead of overall ANOVA followed by post-hoc tests.

Question 19

Define planned contrasts?

Answer 19

Planned contrasts can test complex comparisons that involve combinations of groups.

Question 20

What are the 2 advantages of planned comparisons over post-hoc tests?

Answer 20

1. For the same comparison, you are more likely to find a significant difference with a planned comparison that with an equivalent post-hoc test (I.e., they are statistically more powerful)
2. Can design complex comparisons

Question 21

What is an advantage of post-hoc tests over planned comparisons?

Answer 21

1. Let you compare everything with everything else (planned comparisons permit a smaller number of focussed comparisons).

Question 22

What are the rules for planned comparisons?

Answer 22

• you do them instead of an overall ANOVA (not as well as).
• the maximum number of planned comparisons you can have is the number of groups -1.
• your contrast coefficients must sum to zero.