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

Explanation

We know, `P(X)` should be between `0 and 1`.

Also, sum of all the probablities in a probablity distribution should be 1.



(i) Here, sum of all probablities is 1 and all probablities are between 0 and 1.
So, this is a probablity distribution.



(ii) Here, P(X=3) is negative. So, this is not a probablity distribution.



(iii) Here, sum of all probablities is `0.9` which is less than 1.So, this is not a probablity distribution.


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