When submitting an application, you complete a verbal and math assessment online. Should you do well on that, they might extend an offer for an interview. My interview was one day out in Plano. It consisted of 2 case interviews, a behavioral interview, and they have you complete another math assessment to ensure someone else didn't take it for you. I wouldn't say the interviews were that difficult, but from what I understand the positions are fairly competitive so there is little margin for error.