Hi Pushpa. I went through the group interview process last year in October when MAC started their Christmas help interviewing. Basically, there are about 8-9 people in each group. Everyone goes to a room where they all sit around a table, kind of like a boardroom meeting. There are two managers there that also sit at the table. They basically ask everyone to introduce themselves and tell everyone a little bit about themselves.
After that come the very general type questions: What do you know about MAC? Why do you want to work for MAC? How did you become interested in this field? What does good customer service consist of? What would your best friend say is your best quality? What inspires you? etc, etc....
The kicker is, that the questions are not asked to each individual...they are just thrown out there. You HAVE to make yourself stand out by answering the questions first. Now, imagine 8-9 people trying to do this at the same time! Yeah, it can be pretty unnerving, especially for someone who is shy.
Also, a BIG thing that they look at is if you fit in the "MAC image". In other words, can you look and act the part -- makeup, dress, great attitude, enthuastic about makeup artistry and if you are generally trendy....and NO, they don't look at looks, like a lot of people think. At least, I don't think so.
The group interview is very general. I think it is a way for them to weed out tons of applications without having to do a ton of traditional interviews.