Multinomial Logistic Regression With 3 predictors X1, X2, X3 and 3 possible values for the dependent variable Y: A, B, C

When you build the model before getting the results you aren't sure if X3 should be in the model.

X3 is significant for ln(Pb/Pa) , but is insignificant for ln(Pc/Pa)

Will you include X3 in the model?