Filtering reduces noise if signal
stable
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Suppose I(i) = I+n(i), I(i+1) = I+n(i+1)
I(i+2) = I+n(i+2).
•
Average of I(i), I(i+1), I(i+2) = I +
average of n(i), n(i+1), n(i+2).
•
When there is no noise, averaging
smooths the signal.
•
So in real life, averaging does both.