Problem-Solving and Data AnalysisEasyEstimating a population count from a sample
Problem-Solving and Data Analysis practice question
A quality inspector randomly selects 80 light bulbs from a shipment of 5,000 and finds that 4 of them are defective. Based on the sample, which of the following is the best estimate of the number of defective bulbs in the whole shipment?
- A. 250Correct
- B. 4
- C. 62
- D. 400
Answer: A. 250
In the sample, 4/80 = 5% of bulbs are defective. Applying that rate to the shipment: 5% of 5,000 = 250.
Why the other answers are wrong
- B. 4
- 4 is the number of defective bulbs in the SAMPLE. The shipment is much larger, so scale the sample rate up.
- C. 62
- 62 is roughly 5,000 / 80 — the number of samples that would fit in the shipment, not a defect count.
- D. 400
- 400 is 8% of 5,000. The sample rate is 4/80 = 5%, not 8%.
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