How dies the ES/SD relate to group size?
- Thread starter Linko
- Start date
Technically, the standard deviation is not an average. It is the square root of the variance.
fyrewall
Banned
Relatively small standard deviation or SD do not matter that much at short ranges like 100 yards. Looking at your targets & data sort of indicates the best 2 groups occurred with the largest SD values. *** edit ** 2 or more events - 5 shots fired with the Magneto speed hanging from the barrel to get the numbers followed by another without the Magneto speed to get a group(s) and then linking all? (ie. I & Joe R, yotehater -- don't think this is valid)
As an indication of what the SD shows - it is the square root of another value called the variance. The variance is the sum of a bunch of values, each bunch being a velocity minus the average squared plus the same thing for the other velocities. Or (((vel. 1 - average)**2) + ((vel. 2 - average)**2 + more of the same until last velocity ) / number of cases, in this it would be 5.
The velocity less average is squared, because in some instances it would be a negative value and the objective is to get an indication of differences apart from the average. Finally, the SD comes out of all this as the square root of the variance and the SD gives an indication of how far the data points (velocities) are from the average.
From all this stuff you can see the ES is one value and the SD is a measure of a group of values and to me this is "how they relate"
I have always had problems with those devices that have one button for all functions, probably because I don't like using other peoples logic that is probably driven by economic reasons to make the thing as cheap as possible. Did your device transmit the data directly to the source printout?
I have always been cautious about data transmission, not that I suspect the process but I think the management of the stuff received is suspect to confusion and error.
I ran your data on my Excel spread sheet for series 19 and came up with:
2884,2902,2886,2895,2897
Ave = 2892, Min = 2884, Max = 2902, ES = 18 -- the same
but
my average = 2892.8, rounded would be 2893
my variance = 46.16, my SD = 6.79 -- not the same
For me an extreme spread of 18 fps for any of the bullets that I shoot at ranges up to 1/2 mile at targets like steel plates or rodents would not be important. I get more hits on supine rodents vs. standing rodents giving an indication that wind effects are a greater consideration.
********* edit
possibly, would your SD of 7.6 be a transposed error of 6.79 ?, it appears that you are on the right track for record keeping and the rest of it.
As an indication of what the SD shows - it is the square root of another value called the variance. The variance is the sum of a bunch of values, each bunch being a velocity minus the average squared plus the same thing for the other velocities. Or (((vel. 1 - average)**2) + ((vel. 2 - average)**2 + more of the same until last velocity ) / number of cases, in this it would be 5.
The velocity less average is squared, because in some instances it would be a negative value and the objective is to get an indication of differences apart from the average. Finally, the SD comes out of all this as the square root of the variance and the SD gives an indication of how far the data points (velocities) are from the average.
From all this stuff you can see the ES is one value and the SD is a measure of a group of values and to me this is "how they relate"
I have always had problems with those devices that have one button for all functions, probably because I don't like using other peoples logic that is probably driven by economic reasons to make the thing as cheap as possible. Did your device transmit the data directly to the source printout?
I have always been cautious about data transmission, not that I suspect the process but I think the management of the stuff received is suspect to confusion and error.
I ran your data on my Excel spread sheet for series 19 and came up with:
2884,2902,2886,2895,2897
Ave = 2892, Min = 2884, Max = 2902, ES = 18 -- the same
but
my average = 2892.8, rounded would be 2893
my variance = 46.16, my SD = 6.79 -- not the same
For me an extreme spread of 18 fps for any of the bullets that I shoot at ranges up to 1/2 mile at targets like steel plates or rodents would not be important. I get more hits on supine rodents vs. standing rodents giving an indication that wind effects are a greater consideration.
********* edit
possibly, would your SD of 7.6 be a transposed error of 6.79 ?, it appears that you are on the right track for record keeping and the rest of it.
Last edited:
If you're monitoring head expansion, you'll know if you're at the top end.
retired
Banned
top of a node is not necessarily any where near max load...tho there maybe a node near max. they are independent of each other.
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