medium · GMAT Quant
A semiconductor quality-control process evaluates microchip processing delays across two production lines that share the same mean delay. Batch A contains n_1 = 10 microchips with a population variance of σ_1^2 = 12 square milliseconds. Batch B contains n_2 = 15 microchips with a population variance of σ_2^2 = 22 square milliseconds.
What is the combined population variance of processing delays for the 25 microchips?
- 17.0
- 18.0
- 18.6
- 450.0
- 22.5
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