get_reading_score_data = function(){
    ##
    ## xpdf ../EBook/Applied_Linear_Models_with_R.pdf -z 200 100 &
    ##
    additional_directed = c(24, 53, 57, 43, 56, 58, 59, 71, 52, 43, 62, 49, 54, 61, 57, 44, 33, 67, 46, 49, 43)
    no_additional_activities = c(42, 20, 55, 43, 85, 28, 55, 46, 48, 26, 10, 62, 17, 37, 60, 33, 53, 41, 42, 19, 37, 54, 42)

    df_1 = data.frame(score=additional_directed, additional_activities=rep('YES', length(additional_directed)))
    df_2 = data.frame(score=no_additional_activities, additional_activities=rep('NO', length(no_additional_activities)))
    DF = rbind(df_1, df_2)
}