Question

A student who used a regression model that included indicator variables was upset when receiving only the following output on the multiple regression printout: X TRANSPOSE X SINGULAR. What is a likely source of the difficulty

Answer 1

Answer:

This is a multicolinearity problem and the student should determine the variable(s) that cause(s) the problem and remove it.

Explanation:

This information means that there exists a linear combination between the independent variables. The problem might have developed due to multicolinearity producing almost perfectly linearly dependent columns.

This could also be as a results of single matrix created when the student use an incorrect indicator variables and included an additional indicator column which created linearly dependent columns.