Week 6 Flashcards
(45 cards)
What is ANOVA?
Analysis of Variance, a parametric test that compares mean scores across conditions with 2 or more conditions
ANOVA is an extension of a t-test.
What is a FACTOR in ANOVA?
The independent variable in a study
Example: In a study of drink type on reaction time, drink type is the factor.
What is a LEVEL in ANOVA?
The separate conditions present within the factor
For example, caffeinated coffee, decaf, and water are three levels of the factor ‘drink type’.
What defines a One-way ANOVA?
An ANOVA with only one factor consisting of any number of levels, requiring independent samples for each level
Example: One group drinks caffeinated coffee, another drinks decaf, and a third drinks water.
What are the assumptions of ANOVA?
Homogeneity of variance, normally distributed data, and continuous dependent variable
Example of dependent variable: revision time measured in hours.
What happens when assumptions of ANOVA are violated?
ANOVA is robust with equal group sizes but not with unequal numbers
Equal group numbers can help with violation of homogeneity of variance.
What does a Two-way ANOVA involve?
An ANOVA with two or more factors
Example: drink type and quality of sleep as factors in a study.
What are the types of ANOVA by design?
Within-Subjects, Between-Subjects, Mixed Designs
These determine how data is entered into SPSS and what type of ANOVA is selected.
What are the three statistics obtained from a Two-way ANOVA?
Main effect of IV1, main effect of IV2, and interaction between IV1 and IV2.
What is a research question for a Two-way ANOVA example?
Is there a significant difference in statistic test scores based on caffeine and sleep?
What are the levels of the independent variables in the caffeine and sleep example?
Caffeine: 3 levels (coffee, decaf, water); Sleep: 2 levels (slept, not slept).
What is a main effect in ANOVA?
The difference in the dependent variable between the conditions of an independent variable.
What does a significant main effect of drink indicate?
There is a significant difference in stats exam scores among the drink conditions
Example: F(2, 10) = 17.38, p < .05.
What does a non-significant main effect of sleep indicate?
There is no significant difference in stats exam scores between sleep conditions
Example: F(1, 5) = 3.16, p = .136.
What is an interaction effect in ANOVA?
The effect of one independent variable depends on the level of another independent variable.
What does a significant interaction effect indicate?
Test scores depend on the interaction of both drink and sleep conditions
Example: F(2, 10) = 9.08, p = 0.006.
What are post-hoc tests used for in ANOVA?
To understand main effects when the independent variable has more than 2 levels.
What should be checked in post-hoc test results?
Check if the ‘Sig.’ column is less than .05 to infer a difference between conditions.
Fill in the blank: ANOVA is a ______ test.
parametric
True or False: A significant main effect tells us where the differences are.
False
What do post-hoc tests following ANOVA display?
All possible comparisons and the associated statistical significance
In post-hoc tests, how do you determine if there is a significant difference between conditions?
If the ‘Sig.’ column is less than .05 (i.e. if p < .05)
What can be inferred if the ‘Sig.’ value is less than .05?
There is a difference between the conditions
How are the comparisons in post-hoc tests presented?
Comparisons are repeated both ways round
