Q. 145.0( 1 Vote )

# A die is tossed t

Answer :

As success is considered when we get an odd number when we roll a die.

As die is rolled twice , so we can get no success or a single success or we can get odd both the times an odd number.

If X is the random variable denoting the success then X can take value 0,1 or 2

∵ P(getting an odd number in a single rolling of die) = 3/6 = 1/2

As rolling a die is an independent event:

∴ P(getting an odd on first roll and probability of getting odd on second roll)=P(getting an odd on first roll) x P(getting an odd on second roll)

Note: P(AՈB) = P(A)P(B) where A and B are independent events.

∴ P(X=0) = P(even number on first throw) x P(even on second throw)

=

P(X=1) = P(even number on first throw) x P(odd on second throw) +

P(odd number on first throw) x P(even on second throw)

=

P(X=2) = P(odd number on first throw) x P(odd on second throw)

=

Now we have p_{i} and x_{i.}

Let’s proceed to find mean and variance.

Mean of any probability distribution is given by Mean = ∑x_{i}p_{i}

Variance is given by:

Variance = ∑ x_{i}^{2}p_{i} – (∑x_{i}p_{i})^{2}

∴ first we need to find the products i.e. p_{i}x_{i} and p_{i}x_{i}^{2} and add them to get mean and apply the above formula to get the variance.

Following table representing probability distribution gives the required products :

∵ Variance = ∑ x_{i}^{2}p_{i} – (∑x_{i}p_{i})^{2}

∴ Variance =

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