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CA Foundation · Quantitative Aptitude · Theoretical Distributions

A binomial variate has parameters n = 10 and p = 0.5. Which statement about its distribution is correct?

The distribution is symmetric. When p equals 0.5, the probabilities of k successes and n−k successes are equal, so the shape is symmetric about the mean of 5, and skewness is zero. Variance of 2.5 is below the mean.

  1. AIt is positively skewed
  2. BIt is negatively skewed
  3. CIt is symmetricCorrect
  4. DIts variance is greater than its mean

Explanation

When p = 0.5 the binomial distribution is symmetric about n/2 = 5. Skewness is (q − p)/√npq = 0. Variance = 2.5 which is less than the mean of 5, so the last option is false.

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