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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. Indicate the correct answer for the combination from the following regarding the conditions for the applicability of a binominal distribution:

    (a) There are n independent trials

    (b) Each trial has only two possible outcomes

    (c) The probabilities of two outcomes do not remain constant

    (d) The trials are independent

    Which of the following options is correct?

  5. 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.”

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