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Computing the Variance and Standard Deviation of a Discrete Random Variable

 

Example:  Find the variance and standard deviation of the discrete random variable given in the table below.

 

x

P(X = x)

0

0.008

1

0.096

2

0.384

3

0.512

 

Using the data from above table, store x into L1 and  P(x) into L2, press STAT, highlight CALC. Select 1:1Var Stats, press ENTER and press 2nd [L1] , 2nd [L2] ENTER. The population standard deviation of the discrete random variable, , is .6928.

 

 

To find the variance, you must use the standard deviation. Since the variance is equal to the standard deviation squared, type in .69282 and press the key. The variance of the discrete random variable is .4799955.