hard · GMAT Quant
An operations supervisor tracks worker daily output across three independent units. Unit A has 10 workers with mean output 100 and population variance 25. Unit B has 10 workers with mean output 110 and population variance 30. Unit C has 20 workers with mean output 105 and population variance 20.
What is the population variance of the combined output of all 40 workers?
- 23.75
- 25
- 36.25
- 37.18
- 1,450
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