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Three numbers are selected at random (without replacement ) from first six positive integers. Let X denote the largest of the three numbers obtained. Find the probability distribution of X. Also, find the mean and variance of the distribution.

 

 

 

 
 
 
 
 

Answers (1)

As the first 6 positive integers are 1,2,3,4,5,6 so the variate X takes values 3,4,5 and 6. The probability distribution is given as :

X 3 4 5 6
P(X)

\frac{1}{20}

\frac{3}{20} \frac{6}{20} \frac{10}{20}

 

Now the mean of the distribution \mu = \sum x p(x) = \frac{105}{20} = \frac{21}{4}

Variance of the distriburtion = \sigma ^2= \sum x^2 p(x) - \mu ^2 = \frac{567}{20}- \frac{441}{16} = \frac{2268-2205}{80}= \frac{63}{80} 

Posted by

Ravindra Pindel

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