library(tidyverse)

Read data and select

   Leeftijd           Geslacht         KT.MediaMarkt        KT.BOL        KT.Coolblue  
 Length:83          Length:83          Min.   : 1.000   Min.   : 3.000   Min.   : 2.0  
 Class :character   Class :character   1st Qu.: 4.000   1st Qu.: 7.000   1st Qu.: 8.0  
 Mode  :character   Mode  :character   Median : 6.000   Median : 8.000   Median : 8.0  
                                       Mean   : 5.452   Mean   : 7.724   Mean   : 7.5  
                                       3rd Qu.: 7.000   3rd Qu.: 9.000   3rd Qu.: 8.0  
                                       Max.   :10.000   Max.   :10.000   Max.   :10.0  
                                       NA's   :52       NA's   :54       NA's   :75

Explore data

Boxplots

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