within-groups anova
DESCRIPTION
Within-Groups ANOVA. Chapter 13. One-Way Within-Groups ANOVA. Similar to paired-samples t -tests Same participants do something multiple (more than 2) times Are used when we have one IV with at least 3 levels, a scale DV, and the same participants in each group. - PowerPoint PPT PresentationTRANSCRIPT
Within-GroupsANOVA
Chapter 13
One-Way Within-Groups ANOVA
> Similar to paired-samples t-tests• Same participants do something multiple
(more than 2) times> Are used when we have one IV with at
least 3 levels, a scale DV, and the same participants in each group
Benefits of Within-Groups ANOVA
> We reduce error due to differences between the groups.
> We know that the groups are identical for all of the relevant variables because each group includes exactly the same participants.
> We are able to reduce within-groups variability due to differences for the people in our study across groups.
Steps of Hypothesis Testing
> Step 1. Identify populations, distribution, and assumptions.
> Step 2. State the null and the research hypotheses.
> Step 3. Determine characteristics of the comparison distribution.
> Step 4. Determine critical values.> Step 5. Calculate the test statistic.> Step 6. Make a decision.
Formulae
1 groupsbetween Ndf
1ndf subjects
))(( subjectsbetweenwithin dfdfdf
1 totaltotal Ndf
2)( GMXSStotal
2)( GMMSSbetween
2)( GMMSS tparticipansubjects
subjectsbetweentotalwithin SSSSSSSS between
betweenbetween df
SSMS
subjects
subjectssubjects df
SSMS
within
withinwithin df
SSMS
within
subjectssubjects MS
MSF
within
betweenbetween MS
MSF
Effect Size
> R2 can be calculated for this type of ANOVA, too!
)(2
subjectstotal
between
SSSS
SSR
> Post hoc test to identify where you have differences if your F is significant
> You need to calculate the standard error before using the Tukey HSD test
Tukey HSD
N
MSs withinM
MS
MMHSD
)( 21
> Matched groups use different people who are similar on all of the variables that we want to control.
> We can analyze our data as if the same people are in each group, giving us additional statistical power.
Matched Groups