CA Foundation · Quantitative Aptitude · Theoretical Distributions
The monthly electricity consumption of households in a Jaipur colony is normally distributed with mean 200 units and standard deviation 40 units. Given that the area under the standard normal curve between Z = 0 and Z = 1.5 is 0.4332, what proportion of households consume more than 260 units?
The proportion is 0.0668. Converting 260 units gives Z = (260 - 200)/40 = 1.5, and the upper tail beyond Z = 1.5 equals 0.5 minus 0.4332, which is 0.0668. Using 0.9332 would give the proportion below 260 instead.
- A0.0668Correct
- B0.4332
- C0.9332
- D0.1332
Explanation
Z = (260 - 200)/40 = 1.5. P(X > 260) = P(Z > 1.5) = 0.5 - 0.4332 = 0.0668. The option 0.9332 is P(Z < 1.5), which is the wrong tail, and 0.4332 forgets to subtract from 0.5.
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