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Re: statistical fluctuations



In a private message Bernard Cleyet asked:

> p.s. why "stat. flucts."?  I think subtracting
> background is more appropriate.

In my illustration one chip recorded 47 tracks
(signal plus background) while another recorded
37 (background). I subtract and obtain signal
equal to 10. But I can not say that signal=10
because both 47 and 37 would fluctuate from
chip to chip. The probability that the true signal
is 10 is very very small in this example.

Now consider the Oriani's method. (His numbers
were actually much larger, I made them small to
focus on fluctuations. Suppose that using his
method (one chip) I observe 37 before the
experiment and 47 after the experiment. I conclude
that the signal is 10. Yes, I do not expect that the next
experiment will yield the same signal but the result
will always be positive or zero. Is it correct to say
that the standard deviation for the signal should
be sqrt(10), in this illustration? I am not certain.
Ludwik Kowalski