Repeated measure one-way ANOVA Flashcards
repeated measures one-way ANOVA
within participants design
one-way ANOVA
when we have 1 IV with more than 2 levels
t^2
F value
between IV level variance
- manipulation of IV
- experimental error (random)
within IV level
- experimental error (random)
what does variance within IV levels for repeated measures NOT include
variance due to individual differences
- includes ONLY error variance
H0
- no difference between population means under different levels of IV
F formula
- repeated measures designs will result in higher F values compared to independent design as smaller variance within levels due to not including individual differences … dividing variance between by a smaller number… further from 0
assumptions of repeated measures one-way ANOVA
- normality
- sphericity (homogeneity of covariance) (RM only)
- equivalent sample size
Sphericity
- homogeneity of covariance
- the variance in difference scores under each IV level pair should be reasonably equivalent
Mauchly’s
- tests Sphericity
- H0: no difference between the co variances under each IV level pair (homogeneity)
- p < .05 reject null (shows heterogeneity)
what is the correction for Mauchly’s test
Greenhouse-Geisser
what is the non-parametric equivalent if assumptions are violated
Friedman Test
RM ANOVA: SPSS OUTPUT Mauchly’s
RM ANOVA: SPSS OUTPUT TABLE : IF M IS NOT SIGNIFICANT
RM ANOVA: SPSS OUTPUT TABLE : IF M IS SIGNIFICANT
SPSS OUTPUT - GENERAL
Model sum of squares (SSm)
variance between IV levels (incl. variance due to manipulation of he IV and error)
Residual sum of squares (SSr)
variance within IV levels (incl. only error variance, but not variance due to individual differences)
MSm formula
SSm/dfM
F : SPSS output
MSm/MSr
degrees of freedom for repeated measures one-way ANOVA
(dfM = k -1)
dfR = dfM x (n-1)
k = number of IV levels
n = number of participants
- note if you use corrected d.f.
post-hoc test repeated measures one-way ANOVA
- to asses which IV level means differ
- only when F value significant
- Bonferroni
Bonferroni SPSS output
effect size table
memorize
partial eta^2 formula for repeated measures
be able to do by hand
Cohen’s d formula
be able to do by hand
- always report even if not significant, if not significant don’t talk about effect size
advantages of repeated measures vs independent
- requires fewer participants
- error variance within IV levels reduced as no individual differences
- more sensitive/powerful than independent so easier to find significant difference (void type II error)
disadvantages of repeated measures vs independent
- order effects e.g. practice effect, fatigue effects, sensitization, carry-over effects
- counterbalance to spread out impact of order effects, not get rid
sensitization
p’s start to work out aim of study and behave in a particular way to annoy or please experimenter
may be unconscious
alternatives to counterbalancing
- fatigue- shorter experiments
- sensitization - intervals between IV level exposure
- practice - so order effects already exist when start study do pre-study practice
- carry-over effects - include a control group
note
can be used for infinite number of levels as long as only one IV
write up one way ANOVA: design
- IV: its levels, sunject design, steps taken to eliminate confounds (e.g. counterbalancing, random allocation)
- DV
one-way ANOVA results: step one: descriptive statistics in the table
- measure of central tendency: mean
- measure of spread: standard deviation
- interval estimate: CIs for upper and lower limit
one-way ANOVA: step 2: results write up
- refer to descriptive statistics table
- state test used
- test statistic: : F(dfM, dfR) = _.__, p = .___ (*)
- if assumption for homogeneity has been violated (Levene’s for independent, Mauchly’s for repeated measures) state what correction you use after statistic (Welch or Greenhouse-Geisser)
- state if results were significantin next sentance with directionality if so
- effect size as partial eta squared as percentage if significant *if not report after test statistic
one-way ANOVA: step 3: post hoc as part of results
- if significant do post-hoc write up
- Tukey HSD for between-subjects
- Bonferroni for within-subject