Systems Operator applicants have rated the interview process at California ISO with 5 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 68.6% positive. This is according to Glassdoor user ratings.
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Four stage interview with an assessment with each interview with different panels. A little repetitive but should weed out people who are unqualified and maintain compatible individuals. Extremely technicial interview as well