CA Foundation · Quantitative Aptitude · Theoretical Distributions
The monthly electricity consumption of households in a Nagpur colony is normally distributed with mean 220 units and standard deviation 40 units. Given P(0 < Z < 1.5) = 0.4332, what proportion of households consume more than 280 units?
The proportion is 0.0668. The standardised value for 280 units is (280 − 220)/40 = 1.5. The area above Z = 1.5 equals 0.5 minus the table area 0.4332, giving 0.0668 of households consuming more than 280 units.
- A0.0668Correct
- B0.4332
- C0.9332
- D0.1332
Explanation
Z = (280 − 220)/40 = 1.5. P(X > 280) = P(Z > 1.5) = 0.5 − 0.4332 = 0.0668. The option 0.9332 is P(Z < 1.5), which is the proportion consuming less than 280 units, so it is wrong.
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