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Question

Let {X i, i ≥ 1} be independent and identically distributed random variables with (X i= 1) = p = 1 - P(X i= 0), S n=  X i. The distribution of S nis?

This question was previously asked in
SSC CGL 2018 (Tier 2) Statistics Previous Year Paper (22-feb-2018)
The correct answer is

Binomial distribution with parameter n and p

Each \(X_i\) takes value 1 with probability \(p\) and 0 with probability \(1-p\), so \(X_i \sim \text{Bernoulli}(p)\).

The sum of \(n\) i.i.d. Bernoulli\((p)\) variables counts the number of successes in \(n\) independent trials, which by definition follows a Binomial distribution with parameters \(n\) and \(p\), i.e. \(S_n \sim B(n,p)\).

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Similar Questions

  1. If X has Binomial distribution with parameters n and p such that np =λ, then \(\mathop {\lim }\limits_{n \to \infty } b\left( {x,n,p} \right);x = 0,1,2,.....\) is equal to:

  2. If the independent random variables X,Y are Binomially distributed with n = 3, p = \(\dfrac{1}{3}\)  and n = 5, p =  \(\dfrac{1}{3}\)  respectively, then the probability of (X + Y ≥ 1) is:

  3. A random variable X is binomially distributed with parameter n = 25 and p = 0.2. The skewness of the variable X is


Important Questions from Binomial Distribution

  1. In a Binomial distribution, the mean is three times its variance. What is the probability of exactly 3 successes out of 5 trials?

  2. If mean and variance of a Binomial variate X are 2 and 1 respectively, then the probability that X takes a value greater than 1 is

  3. For Binomial distribution, n = 10 and p = 0.6, E(X 2) (second moment about origin) is:

  4. Find out the fallacy if any in the statement:

    “The mean and the variance of a binomial distribution is 16.2 and 29.4 respectively.”

  5. If log e(x) is normally distributed with mean 1 and variance 4, then P(0.5 < x < 2) is:

    (where the area between z = 0 and z = 0.25 is 0.0987 and the area between z = 0 and z = 0.5 is 0.1915)

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