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Question

For a Binomial distribution with mean 6 and standard deviation \(\sqrt{2}\), what is the value of P(X = 0) ?

This question was previously asked in
NDA 2 2026 GAT Question Paper (13-Sep-2026)
The correct answer is

\((1/3)^9\) 

To solve for \(P(X = 0)\) in the given binomial distribution, we need to use the properties of a binomial distribution and the information provided about its mean and standard deviation.

The parameters of a binomial distribution are:

  • \(n\): Number of trials
  • \(p\): Probability of success on a single trial

The mean \(\mu\) of a binomial distribution is given by:

\(\mu = n \cdot p\)

The standard deviation \(\sigma\) of a binomial distribution is given by:

\(\sigma = \sqrt{n \cdot p \cdot (1-p)}\)

From the problem, we know:

  • The mean \(\mu = 6\)
  • The standard deviation \(\sigma = \sqrt{2}\)

We set up the equations using the given mean and standard deviation:

\(n \cdot p = 6\) (Equation 1)

\(\sqrt{n \cdot p \cdot (1-p)} = \sqrt{2}\)

Squaring both sides of the second equation gives:

\(n \cdot p \cdot (1-p) = 2\) (Equation 2)

Now, substituting the value of \(n \cdot p\) from Equation 1 into Equation 2:

\(6 \cdot (1-p) = 2\)

\(6 - 6p = 2\)

Solving for \(p\):

\(4 = 6p\)

\(p = \frac{2}{3}\)

Substituting \(p = \frac{2}{3}\) back into Equation 1 to solve for \(n\):

\(n \cdot \frac{2}{3} = 6\)

\(n = 6 \cdot \frac{3}{2} = 9\)

The probability \(P(X = 0)\) is given by the binomial probability formula for \(X = 0\):

\(P(X = 0) = \binom{n}{0} \cdot p^0 \cdot (1-p)^n\)

Where:

  • \(n = 9\)
  • \((1-p) = \frac{1}{3}\)

Therefore,

\(P(X = 0) = (1-p)^n = \left(\frac{1}{3}\right)^9\)

Hence, the value of \(P(X = 0)\) is \(\left(\frac{1}{3}\right)^9\).

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Similar Questions

  1. The occurrence of a disease in an industry is such that the workers have 20% chance of suffering from it. What is the probability that out of 6 workers chosen at random, 4 or more will suffer from the disease?
  2. In a binomial distribution, if the mean is 6 and the standard deviation is \(\sqrt{2}\), then what are the values of the parameters \(n\) and \(p\) respectively?
  3. Let X be a random variable following a binomial distribution whose mean and variance are 200 and 160 respectively. What is the value of the number of trials n?


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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