I have a database with several missing points meaning that the number of data in each column is different. Can I draw the distribution of response value for each independent variable and combine them to come up with the distribution of response variable for the combined conditions? In other words, can I say: P(y|x1&x2&x3)=P(y|x1)&P(y|x2)&P(y|x3)?

I appreciate if somebody respond me.