Self Esteem Score Data for Two-way Repeated Measures ANOVA

Data are the self esteem score of 12 individuals enrolled in 2 successive short-term trials (4 weeks) - control (placebo) and special diet trials.

The self esteem score was recorded at three time points: at the beginning (t1), midway (t2) and at the end (t3) of the trials.

The same 12 participants are enrolled in the two different trials with enough time between trials.

Two-way repeated measures ANOVA can be performed in order to determine whether there is interaction between time and treatment on the self esteem score.

For a worked tutorial on this analysis, see the Datanovia lesson “Repeated Measures ANOVA in R: Compare Means Across Time” (https://www.datanovia.com/learn/biostatistics/anova/repeated-measures-anova-in-r).

data("selfesteem2")

Format

A data frame with 24 rows and 5 columns (stored as a tibble).

id: participant identifier (1 to 12); each participant takes part in both trials.
treatment: the trial, "ctr" (control/placebo) or "Diet".
t1: the self esteem score at the beginning of the trial.
t2: the self esteem score midway through the trial.
t3: the self esteem score at the end of the trial.

The self esteem score is a simulated measure on an arbitrary scale with no real-world units.

Source

A simulated dataset created for teaching two-way repeated measures ANOVA.

Examples

data(selfesteem2)
head(selfesteem2)
#> # A tibble: 6 × 5
#>   id    treatment    t1    t2    t3
#>   <fct> <fct>     <dbl> <dbl> <dbl>
#> 1 1     ctr          83    77    69
#> 2 2     ctr          97    95    88
#> 3 3     ctr          93    92    89
#> 4 4     ctr          92    92    89
#> 5 5     ctr          77    73    68
#> 6 6     ctr          72    65    63

# Two-way repeated measures ANOVA (treatment x time), both within-subjects
selfesteem2_long <- reshape(selfesteem2, varying = c("t1", "t2", "t3"),
                            v.names = "score", timevar = "time",
                            idvar = c("id", "treatment"), direction = "long")
summary(aov(score ~ treatment * factor(time) +
              Error(factor(id)/(treatment * factor(time))),
            data = selfesteem2_long))
#> 
#> Error: factor(id)
#>           Df Sum Sq Mean Sq F value Pr(>F)
#> Residuals 11   4641   421.9               
#> 
#> Error: factor(id):treatment
#>           Df Sum Sq Mean Sq F value Pr(>F)   
#> treatment  1  316.7   316.7   15.54 0.0023 **
#> Residuals 11  224.2    20.4                  
#> ---
#> Signif. codes:  0 ‘***’ 0.001 ‘**’ 0.01 ‘*’ 0.05 ‘.’ 0.1 ‘ ’ 1
#> 
#> Error: factor(id):factor(time)
#>              Df Sum Sq Mean Sq F value   Pr(>F)    
#> factor(time)  2  258.7  129.35   27.37 1.08e-06 ***
#> Residuals    22  104.0    4.73                     
#> ---
#> Signif. codes:  0 ‘***’ 0.001 ‘**’ 0.01 ‘*’ 0.05 ‘.’ 0.1 ‘ ’ 1
#> 
#> Error: factor(id):treatment:factor(time)
#>                        Df Sum Sq Mean Sq F value   Pr(>F)    
#> treatment:factor(time)  2 266.36  133.18   30.42 4.63e-07 ***
#> Residuals              22  96.31    4.38                     
#> ---
#> Signif. codes:  0 ‘***’ 0.001 ‘**’ 0.01 ‘*’ 0.05 ‘.’ 0.1 ‘ ’ 1

Self Esteem Score Data for Two-way Repeated Measures ANOVA

Format

Source

See also

Examples