extremely significantP ≤ 0.001
highly significantP ≤ 0.01
P value ≤ 0.0001 is considered as extremely significant (****), P ≤ 0.001 as highly significant (***), P ≤ 0.01 as very significant (**), P ≤ 0.05 as significant (*) and P > 0.05 as not significant (NS), respectively.