Let the population x obey the normal distribution n (U, σ ^ 2), x1, X2, X3,..., xn be a sample of it, then the variance of the sample mean a is? (need process)

Let the population x obey the normal distribution n (U, σ ^ 2), x1, X2, X3,..., xn be a sample of it, then the variance of the sample mean a is? (need process)

The law of normal distribution is that the mean value x obeys n (U, (σ ^ 2) / N)
Because x1, X2, X3,..., xn all obey n (U, σ ^ 2), the additivity of positive distribution X1 + x2... Xn obey n (nu, n σ ^ 2)
The mean value x = (x1 + x2... Xn) / N, so the expectation of X is u, and the variance D (x) = D (x1 + x2... Xn) / N ^ 2 = σ ^ 2 / n

Elden Ring Premiere

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