[R] R vs SPSS - simple effects analysis in mixed 2x2 ANOVA scheme - same data, different results

[Michael Dewey]

The only people who will be able to help you are people who use both R 
and SPSS as you do not show the result from either. So even though they 
can re-run your R commands they cannot compare them with SPSS.

On 22/05/2016 09:49, Michu Kom wrote:
> down votefavoriteHell
> <http://stats.stackexchange.com/questions/213592/r-vs-spss-simple-effects-analysis-in-mixed-2x2-anova-scheme-same-data-diffe#>
>
> Hello,
>
> I prepared a mixed 2x2 ANOVA design analysis both in SPSS and in R. The
> SPSS script is correct, but in R script there is a mistake somewhere. To
> test that I generated artificial data from a normal distribution to
> simulate the interaction between two independent variables. There were no
> difference between the results in main effects, but results of simple
> effects analysis do not match when comparing between levels of variable
> which introduced repeated measures (GROUP A: PRE vs POST ; GROUP B: PRE vs
> POST).
>
> I would be very thankful if you can help me. The code below will do
> everything for you.
>
> *Here is the code in R which:* - generates the data - calculates mixed
> ANOVA - prepares data to csv format to import to SPSS - performs simple
> effect analysis (there is probably a mistake)
>
> N <- 100
> absMean <- 1
> sdCustom <- 5
>
> grA_pre <- data.frame(ID = seq(N), lvl=rnorm(N, mean=absMean,
> sd=sdCustom), group=factor('A'), stage = factor('pre'))
> grA_post <- data.frame(ID = seq(N), lvl=rnorm(N, mean=-absMean,
> sd=sdCustom), group=factor('A'), stage = factor('post'))
> grB_pre <- data.frame(ID = seq(N+1,2*N), lvl=rnorm(N, mean=-absMean,
> sd=sdCustom), group=factor('B'), stage = factor('pre'))
> grB_post <- data.frame(ID = seq(N+1,2*N), lvl=rnorm(N, mean=absMean,
> sd=sdCustom), group=factor('B'), stage = factor('post'))
>
> gr <- rbind(grA_pre, grA_post, grB_pre, grB_post)
> names(gr)
> head(gr)
> # save set to .csv to import to SPSS
> grSPSS <- reshape(data = gr, timevar = "stage", idvar = c("ID",
> "group"), direction = "wide")
>
> write.csv2(grSPSS, file = "sample2.csv")
>
> library(ggplot2)
> library(plyr)
> library(ez)
> print("Omnibus mixed ANOVA - main effects and interactions")
> ezPlot(data = gr, wid = ID, dv = lvl, between = group, within = stage,
> type = "III", x = group, split = stage, x_lab = "Group", y_lab =
> "Level of experience")
> ezANOVA(data = gr, wid = ID, dv = lvl, between = group, within =
> stage, detailed = TRUE, type = "III")#ezStats(data = gr, wid = ID, dv
> = lvl, between = group, within = stage, type = "III")
>
> print("Simple main effects analysis")
> dataA <- subset(gr, group == "A" )
> dataB <- subset(gr, group == "B" )
> dataPRE <- subset(gr, stage == "pre" )
> dataPOST <- subset(gr, stage == "post" )
> print("GROUP = A: PRE vs POST")
> simpleEffControlANOVA <- ezANOVA(data = dataA, dv = lvl, wid = ID,
> within = stage, detailed = TRUE, type = "III"
> )print(simpleEffControlANOVA)
> print("GROUP = B: PRE vs POST")
> simpleEffControlANOVA <- ezANOVA(data = dataB, dv = lvl, wid = ID,
> within = stage, detailed = TRUE, type = "III"
> )print(simpleEffControlANOVA)
> print("STAGE = PRE: A vs B")
> simpleEffControlANOVA <- ezANOVA(data = dataPRE, dv = lvl, wid = ID,
> between = group, detailed = TRUE, type = "III"
> )print(simpleEffControlANOVA)
> print("STAGE = POST: A vs B")
> simpleEffControlANOVA <- ezANOVA(data = dataPOST, dv = lvl, wid = ID,
> between = group, detailed = TRUE, type = "III"
> )print(simpleEffControlANOVA)
>
> *Here is the code for SPSS Syntax which:* - calculates everything on
> imported data, generated by R
>
> DATASET ACTIVATE DataSet1.
> GLM lvl.pre lvl.post BY group
>   /WSFACTOR=stage 2 Polynomial
>   /METHOD=SSTYPE(3)
>   /POSTHOC=group(TUKEY T3)
>   /EMMEANS=TABLES(group) COMPARE ADJ(BONFERRONI)
>   /EMMEANS=TABLES(stage) COMPARE ADJ(BONFERRONI)
>   /EMMEANS=TABLES(group*stage) COMPARE(group)
>   /EMMEANS=TABLES(group*stage) COMPARE(stage)
>   /PLOT=PROFILE(group*stage)
>   /PRINT=DESCRIPTIVE ETASQ OPOWER HOMOGENEITY
>   /CRITERIA=ALPHA(.05)
>   /WSDESIGN=stage
>   /DESIGN=group.
>
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>
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-- 
Michael
http://www.dewey.myzen.co.uk/home.html