DAT or the Design Aptitude Test has 2 parts DAT I and DAT II and the selection of the interview is done on the basis of the first one. DAT I like a CEED examination has no multiple-choice questions while DAT II covers basic electronics, engineering mechanics, and materials science. The mathematical problems will be such that students from any branch are able to solve them.
The final selection is done on the basis of the total score from the DAT and the PI. The acceptance ratio of CPDM is around 10% as about 200+ students sit for DST and only 20-25 students are selected. One of my friends got selected for the PI round and was asked the following questions
The best way to get selected is to present a unique idea while sounding genuine. Dont bluff as they are quick to catch and you will lose your chance.