Question

to find dereviation of mean​

Answer 1

Step-by-step explanation:

Find the Mean Deviation: Mean Deviation = Σ|x - μ|N = 308 = 3.75. Note: the mean deviation is sometimes called the Mean Absolute Deviation (MAD) because it is the mean of the absolute deviations

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Answer 2

Step-by-step explanation:

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This formula may be derived from what we know about the variance of a sum of independent random variables.

If X1,X2,…,Xn are n independent observations from a population that has a mean μ and standard deviation σ , then the variance of the total

T=(X1+X2+⋯+Xn) is nσ2. Understood.

The variance of T/n must be 1n2nσ2=σ2n. Not understood.

And the standard deviation of T/n must be σ/n−−√ . Of course, T/n is the sample mean x¯ .

Var(X)=1n∑i=1n(xi−μ)2

Var(X)=1n∑i=1n(x2i+μ2−2xiμ)

Var(X)=1n∑i=1nx2i+μ2−2n∑i=1nxiμ

As Sample mean is an unbiased estimate of population mean, we get

Var(X)=1n∑i=1nx2i−μ2

Var(X)=E(X2)−(E(X))2