A fair die is tossed. Let X denote 1 or 3 according as an odd or an even number appears. Find the probability distribution, mean and variance of X.

When a fair dice is thrown there are total 6 possible outcomes.


X denote 1 or 3 according as an odd or an even number appears.


P(appearing of even number on a die) = 3/6 [favourable outcomes {2,4,6}]


P(appearing of an odd number on a die) = 3/6 [favourable outcomes {1,4,3}]


P(X=1) = 3/6 = 1/2


P(X=3) = 3/6 = 1/2


Now we have pi and xi.


Let’s proceed to find mean and variance.


Mean of any probability distribution is given by Mean = ∑xipi


Variance is given by:


Variance = ∑ xi2pi – (∑xipi)2


first we need to find the products i.e. pixi and pixi2 and add them to get mean and apply the above formula to get the variance.


Following table gives the required products :


Required Probability distribution table:-



Mean =


Variance =


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