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If E denotes expectation, the variance of a random variable X is givenby (a) E[X2] − E2[X] (b) E[X2] + E2[X] (c) E[X2] (d) E2[X] |
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Answer» (a) E[X2] − E2[X] The variance of random variable X x2 = E[(X – x)2] Where x is the mean value = E[X] x2 = E[x2] + E[ x]2 - 2 xE[x] = E[x2] + x2 - 2 xx = E[X2 ] – x2 = mean square value – square of mean value |
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