In: Statistics and Probability
Let X~BIN(40,0.1). Let Y=max(0,x-3). FindE[Y].
Since X is binomially distributed over (40,0.1), i calculated the distribution using calculation and table is given below:
| Binomial distribution (n=40, p=0.1) | |||
| f(x) | |||
| x | Pr[X = x] | ||
| 0 | 0.0148 | ||
| 1 | 0.0657 | ||
| 2 | 0.1423 | ||
| 3 | 0.2003 | ||
| 4 | 0.2059 | ||
| 5 | 0.1647 | ||
| 6 | 0.1068 | ||
| 7 | 0.0576 | ||
| 8 | 0.0264 | ||
| 9 | 0.0104 | ||
| 10 | 0.0036 | ||
| 11 | 0.0011 | ||
| 12 | 0.0003 | ||
| 13 | 0.0001 | ||
| 14 | 0 | ||
| 15 | 0 | ||
| 16 | 0 | ||
| 17 | 0 | ||
| 18 | 0 | ||
| 19 | 0 | ||
| 20 | 0 | ||
| 21 | 0 | ||
| 22 | 0 | ||
| 23 | 0 | ||
| 24 | 0 | ||
| 25 | 0 | ||
| 26 | 0 | ||
| 27 | 0 | ||
| 28 | 0 | ||
| 29 | 0 | ||
| 30 | 0 | ||
| 31 | 0 | ||
| 32 | 0 | ||
| 33 | 0 | ||
| 34 | 0 | ||
| 35 | 0 | ||
| 36 | 0 | ||
| 37 | 0 | ||
| 38 | 0 | ||
| 39 | 0 | ||
| 40 | 0 | ||
Now Y = max (0, x-3).
This means that,
Y = 0, for all x 
3
Y = x-3. for all x 
4
| Y | x | P(x) | Y*P(x) | 
| 0 | 0 | 0.0148 | 0 | 
| 0 | 1 | 0.0657 | 0 | 
| 0 | 2 | 0.1423 | 0 | 
| 0 | 3 | 0.2003 | 0 | 
| 1 | 4 | 0.2059 | 0.2059 | 
| 2 | 5 | 0.1647 | 0.3294 | 
| 3 | 6 | 0.1068 | 0.3204 | 
| 4 | 7 | 0.0576 | 0.2304 | 
| 5 | 8 | 0.0264 | 0.132 | 
| 6 | 9 | 0.0104 | 0.0624 | 
| 7 | 10 | 0.0036 | 0.0252 | 
| 8 | 11 | 0.0011 | 0.0088 | 
| 9 | 12 | 0.0003 | 0.0027 | 
| 10 | 13 | 0.0001 | 0.001 | 
| 11 | 14 | 0 | 0 | 
| 12 | 15 | 0 | 0 | 
| 13 | 16 | 0 | 0 | 
| 14 | 17 | 0 | 0 | 
| 15 | 18 | 0 | 0 | 
| 16 | 19 | 0 | 0 | 
| 17 | 20 | 0 | 0 | 
| 18 | 21 | 0 | 0 | 
| 19 | 22 | 0 | 0 | 
| 20 | 23 | 0 | 0 | 
| 21 | 24 | 0 | 0 | 
| 22 | 25 | 0 | 0 | 
| 23 | 26 | 0 | 0 | 
| 24 | 27 | 0 | 0 | 
| 25 | 28 | 0 | 0 | 
| 26 | 29 | 0 | 0 | 
| 27 | 30 | 0 | 0 | 
| 28 | 31 | 0 | 0 | 
| 29 | 32 | 0 | 0 | 
| 30 | 33 | 0 | 0 | 
| 31 | 34 | 0 | 0 | 
| 32 | 35 | 0 | 0 | 
| 33 | 36 | 0 | 0 | 
| 34 | 37 | 0 | 0 | 
| 35 | 38 | 0 | 0 | 
| 36 | 39 | 0 | 0 | 
| 37 | 40 | 0 | 0 | 
| Sum= | 1.3182 | 
Now E[Y] = 
 Y
* P(x)
E[Y] = 1.3182