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Question -

State which of the following are not the probability distributions of a random variable. Give reasons for your answer.



Answer -

(i)

Here we have tablewith values for X and P(X).

As we know the sum ofall the probabilities in a probability distribution of a random variable mustbe one.

Hence the sum ofprobabilities of given table = 0.4 + 0.4 + 0.2

= 1

Hence, the given tableis the probability distributions of a random variable.

(ii)

Here we have tablewith values for X and P(X).

As we see from thetable that P(X) = -0.1 for X = 3.

It is known thatprobability of any observation must always be positive that it can’t benegative.

Hence, the given tableis not the probability distributions of a random variable.

(iii)

Here we have tablewith values for X and P(X).

As we know the sum ofall the probabilities in a probability distribution of a random variable mustbe one.

Hence the sum ofprobabilities of given table = 0.6 + 0.1 + 0.2

= 0.9 ≠ 1

Hence, the given tableis not the probability distributions of a random variable.

(iv)

Here we have tablewith values for X and P(X).

As we know the sum ofall the probabilities in a probability distribution of a random variable mustbe one.

Hence the sum ofprobabilities of given table = 0.3 + 0.2 + 0.4 + 0.1 + 0.05

= 1.05 ≠ 1

Hence, the given tableis not the probability distributions of a random variable.

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