The process begins with an aptitude test containing questions based on logic & reasoning, mathematics and english. There was also an essay to be written (to judge your writing skills) in the second section. They gave two topics to choose from to write the essay on. I had written on 'privatisation of education- good or bad'. They selected only a hand few of the candidates (7 out of 40 or so). After that there was a general interview (Tell about yourself, what do you think is the exact work you'll have to do etc. They also explained in detail the exact job profile in case you were unsure about what work it actually is). They rejected two candidates based on this simple personal interview. After that there were guesstimate questions round. Each candidate was handled by a single person. the person conducting my guesstimate round was very thorough in examining my cv (something i regret to not have worked properly on). He asked me various questions, all based on the information given in my cv. I was given half or so for my guesstimate question. I had to wait for several hours after this round and had gotten rejected by a call at the reception (no feedback, nada). Only 1 candidate amongst those seven selected from the aptitude test had managed to go into the second round of guesstimate question. (i'm unsure how many more rounds are there). But i believe the procedure can extend for more than 1 day.