import seaborn as sns

df = [ (2,4,4,4,5,5,6,6,9,9,9,9,9,9,11,11,11,11,12,12,12,12,14,14,14,14,14,15,15,15,16,16,16,18,18),
       (2,2,2,2,3,3,3,4,5,5,5,6,6,6,7,7,7,7,8,8,8,8,9,9,10,10,14,15,15,15,15,16,16,18,18)]

sns.boxplot(data=df, palette='Set3', linewidth=1.2)