Health Intern applicants have rated the interview process at Mercer with 3 out of 5 (where 5 is the highest level of difficulty) and assessed their interview experience as 100% positive. To compare, the company-average is 68.1% positive. This is according to Glassdoor user ratings.
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Interview process started with an automated computer interview. After this, they do a 2 hour interview where you get to talk to 3-4 different people for 30 min. It seemed to be mostly behavioral questions which I personally prefer.