CA Foundation · Quantitative Aptitude · Theoretical Distributions
A Jaipur firm packs items where each item is independently defective with probability 0.2. In a sample of 15 items, the number of defectives is X. What is the standard deviation of X?
Variance is npq = 15 × 0.2 × 0.8 = 2.4, so the standard deviation is the square root of 2.4, about 1.55. The value 2.4 is only the variance and 3 is the mean.
- AApproximately 1.55
- BApproximately 2.40
- CApproximately 1.73Correct
- DApproximately 3
Explanation
Variance = npq = 15 × 0.2 × 0.8 = 2.4. Standard deviation = √2.4 ≈ 1.55. The 2.40 option is the variance itself, and 3 is the mean.
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