Transparent ruler – like in the good ol’ days [Bioanalytics]

posted by ElMaestro  – Denmark, 2018-11-05 21:43 (847 d 06:47 ago) – Posting: # 19536
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Hi Ohlbe and Hötzi,

Thanks for your qualified opinions.

I am inclined to do this:

lines(c(5.6, 5.6), c(4.1,18), col="green", lwd=6)
lines(c(8, 8), c(4.1,8.8 ), col="red", lwd=6)


where the red line indicates the level of noise (in this case, right of the peak) and the greeen one is the signal. Roughly.

Note that in both cases I quantify s as well as n in one direction from the baseline mean or median or whatever.

Thus I am landing at s:n = (18-4.1) / (8-4.1) = 3.6.
I am not in any way claiming this is better or worse, only that this is my idea of an approach.

If I recall correctly, if you are "a large software vendor" -and I will mention none in particular- you can also do something like:

k=3                   #a miserable sad pointless constant to make s:n look better ??
a=sd (y3[400:714])    #sd of points on the peak
b=sd (y3[800:1000])   #sd of points adjacent to the peak
sn=k*a/b


which gives a result of about 5.:-D
Personally, I would of course always adjust k so that s:n is not less than 10 or so, just to avoid questions. I mean, I care about my data because I am not a nasty person :-D:-D:-D

Pass or fail!
ElMaestro

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