The number of complaints per day X received by a cable TV di
The number of complaints per day, X, received by a cable TV distributor has the probability distribution
x
0
1
2
3
f(x)
0.2
0.3
0.1
0.4
Find the standard deviation of the number of complaints.
Round to three decimal places.
| x | 0 | 1 | 2 | 3 | 
| f(x) | 0.2 | 0.3 | 0.1 | 0.4 | 
Solution
Consider the table:
Thus,          
           
 Var(x) = E(x^2) - E(x)^2 =    1.41      
s(x) = sqrt(Var(x)) = 1.187434209 [ANSWER]
| x | P(x) | x P(x) | x^2 P(x) | 
| 0 | 0.2 | 0 | 0 | 
| 1 | 0.3 | 0.3 | 0.3 | 
| 2 | 0.1 | 0.2 | 0.4 | 
| 3 | 0.4 | 1.2 | 3.6 | 

