Amazon Applied Scientist interview questions

I got the interview from a friend's reference. The recruiter scheduled a phone screen interview first, and I talked to a hiring manger for 40 minutes. At the beginning, she asked me to talked about some of my own research. I think that was just a warming-up before the real question she wanted to ask. The real question is they collected purchase record data at a store for the whole year, so how do you find out the major reason why customers walked into a store. It's an open question, and I think they really want to find somebody to help with this specific question. I was not very sure about what answer they are looking for. I didn't make it to the next step.