Find the mean, variance, and standard deviation of the random variable having the probability distribution given in the following table. (Round your answers to four decimal places.)
Random variable, x | -7 | -6 | -5 | -4 | -3 |
P(X = x) | 0.13 | 0.16 | 0.4 | 0.15 | 0.16 |
Solution :
x | P(x) | x * P(x) | x2 * P(x) |
-7 | 0.13 | -0.91 | 6.37 |
-6 | 0.16 | -0.96 | 5.76 |
-5 | 0.4 | -2 | 10 |
-4 | 0.15 | -0.6 | 2.4 |
-3 | 0.16 | -0.48 | 1.44 |
Sum | 1 | -4.95 | 25.97 |
Mean = X * P(X)
= -4.95
Variance
= X 2 * P(X) - 2
= 25.97 - (-4.95)2 = 1.4675
Standard deviation = = 1.2114
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