DF = data.frame(
    smoker_type=c( rep( 'non', 6 ), rep( 'light', 6 ), rep( 'moderate', 6 ), rep( 'heavy', 6 ) ),
    value=c( 69, 52, 71, 58, 59, 65, 55, 60, 78, 58, 62, 66, 66, 81, 70, 77, 57, 79, 91, 72, 81, 67, 95, 84 )
)