Supervisor applicants have rated the interview process at Northrop Grumman 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 74.2% positive. This is according to Glassdoor user ratings.
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I started with a zoom interview with a panel of 5-6 current employees, then proceeded to have in person site interviews. Overall, the process was moderately difficult. Just be prepared and you'll do just fine.