CA Foundation · Quantitative Aptitude · Theoretical Distributions
Which of the following sets of statistics could describe a Poisson distribution?
Mean 4 and variance 4 could describe a Poisson distribution, because in a Poisson distribution the mean and variance are both equal to the parameter m. The other options have unequal mean and variance, which rules out Poisson.
- AMean 5, variance 3
- BMean 4, variance 4Correct
- CMean 3, variance 5
- DMean 2, variance 6
Explanation
A Poisson distribution has its mean equal to its variance, both being m. Only mean 4 and variance 4 satisfy this. The other pairs have unequal mean and variance, so they cannot be Poisson. Mean 5 and variance 3 would suit a binomial, since variance is less than mean.
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