medium · GMAT Quant
A customer service operation tracks call durations across two work shifts. The morning shift records 40 calls with an average duration of 6 minutes and a duration variance of 9 square minutes. The evening shift records 10 calls with an average duration of 6 minutes and a duration variance of 4 square minutes.
What is the variance of call durations for all 50 recorded calls combined?
- 6.5
- 8.0
- 8.2
- 13.0
- 400.0
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