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- Thread starter g.lemaitre
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Edit: pay attention to this line in particular.

Beware:The average of the squares, [itex]\langle j^2 \rangle[/itex], isnotequal, in general, to the square of the average, [itex]\langle j \rangle ^2[/itex]

This tells you very explicitly what the interpretation of both quantities should be.

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jedishrfu

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so the <j^2> means the average of the squares of j values

and <j>^2 is the square of the average of j values

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{j^2} where j is 2,3,4 would be the average of 4 9 16 hence a little above 9 whereas {j}^2 would be 9 exactly, right?

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Otherwise, yes, you have the basic idea now. You should be accustomed to seeing [itex]\langle j^2 \rangle - \langle j \rangle^2 = \sigma_j^2[/itex] as well. This is one formula for the variance.

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