CA Foundation · Quantitative Aptitude · Theoretical Distributions
For a Poisson distribution, which one of the following statements is correct?
In a Poisson distribution the mean and the variance are both equal to the parameter m. Hence the mean equals the variance. The other statements fail because they imply different values for mean and variance, which is not true for a Poisson distribution for general m.
- AMean is greater than variance
- BMean is equal to varianceCorrect
- CVariance is the square of the mean
- DMean is the square of the variance
Explanation
A Poisson distribution with parameter m has mean m and variance m, so the two are equal. Option C would hold only when m = 1 and is not a general property. Options A and D contradict the equality of mean and variance.
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