9 Classification


The main application of logistic regression is the solution of binary classification problems.


One of the main applications of a logistic regression model is to classify the qualitative variable according to the value taken by the predictors. To achieve this classification, it is necessary to establish a threshold of probability at which the variable is considered to belong to one of the levels.

For example, an observation can be assigned to group 1 if P(Y=1|X)>0.5 and to group 0 otherwise. In that case, the threshold is 0.5:

ˆY={1If ˆπ=P(Y=1|X)>0.5,0If ˆπ=P(Y=1|X)<0.5