Did not hear back from months, then got an email 3 months later asking for a call. recruiter told me she wanted to discuss the position in more detail and wanted to see if I had a writing sample I could provide. I suggested that we have a brief call, so we could see what was required, and after, I'd be happy to provide a sample--would be easier to provide something that was appropriate after that call. (in this time I was also told by a friend that research positions at McKinsey were not well respected from within). She started the call asking about my 2 most recent positions. I spoke about them, even focused on my communications and writing experience. Then said to me that 'as I expected, you are not qualified for the position." And that was the end of it.

Interviews are done in rounds depending on the job you apply to. A round can have a single or multiple interviews. They also give access to a website with prep material.