Planned Contrasts and Repeated Measures (Within-Subjects) ANOVA Week 10

Question 1

What are the advantages of using planned contrasts over post hoc tests?

Answer 1

You are more likely to find a significant difference; they are statistically more powerful

Question 2

What are the disadvantages of using planned contrasts over post hoc tests?

Answer 2

You are limited in what you can do and can only ask (number of groups) - 1 questions

Question 3

What is the difference between between-subjects and within-subjects ANOVA?

Answer 3

Between-Subjects is groups split into two conditions. Within-Subjects is when everyone goes through both conditions.

Question 4

What are post hoc tests?

Answer 4

Tests that you carry out after you have obtained a significant F and want to locate the source of it

Question 5

What is the maximum number of planned contrasts can you do?

Answer 5

number of groups - 1

Question 6

What must the contrast coefficients sum up to?

Answer 6

0

Question 7

List two problems with repeated measures/within subjects design

Answer 7

• Drop outs: if you do not obtain a score from any subject, you have to remove all of the subjects data from the analysis
• Practice/order/carry over effects

Question 8

How do you fix practice effects?

Answer 8

Randomise the testing order - make sure that different subjects receive the treatments in different orders. This makes sure that order effects are random but does NOT remove the entire problem

Question 9

What is meant by single factor within subjects?

Answer 9

One person contributes to each level of the independent variable

Question 10

Planned contrasts are good when…

Answer 10

You have very specific and directional hypotheses that is not exploratory

Question 11

Post hoc tests are good when…

Answer 11

you have a significant F and you are just exploring the data

Question 12

What is a planned contrast?

Answer 12

Specific hypothesis tests involving sub groups of your experiment carried out instead of an ANOVA

Question 13

Do you use planned contrasts and ANOVA?

Answer 13

No, you use one instead of an ANOVA.

Question 14

What are the costs of using planned contrasts?

Answer 14

You are limited in what you can do. You can only ask one less than the total amount of groups you can e.g if you have 4 groups you can only ask 3 questions. Independence is also another limitation.

Question 15

Are you more likely to find a significant difference with a post hoc test or a planned contrast?

Answer 15

Planned contrast- they’re statistically more powerful and you can design complex comparisons

Question 16

What is the advantage of post hoc tests?

Answer 16

You can compare everything with everything else

Question 17

What is a disadvantage of post hoc tests?

Answer 17

You lose statistical power when you compare everything with everything else

Question 18

List two advantages of within-subjects design

Answer 18

• Individual differences is removed

- fewer subjects are needed to obtain the same amount of data

Question 19

What is meant by single-factor/one-way?

Answer 19

Theres is only one independent variable