Quote:
Originally Posted by philjs
The diagram mc1 found is better than the one I found (since it has more dots, ie. the sample size is larger) but the above statement is wrong.
Statistically speaking, the mean distances of all of the dots/shots in the two left diagrams, from their cluster center, are very similar (that is the standard deviations of the shots/dots around each cluster center are very similar) BUT the mean distances of all of the dots/shots from the center of the target are not.
The mean center of the cluster of dots/shots in the accurate-labeled diagram IS the target (but the standard deviation is sufficiently large that they are not precise). If the target is the object center then each of the dots/shots in the not accurate-labeled diagram ALL have very large mean distances (though the standard deviation of those dots/shots from each other may not differ from the accurate-labeled diagram).
The clustering of the shots/dots, regardless of the accuracy with regards to the center of the target, show that they are definitely NOT random.
I'm enjoying the discussion, folks!
Phil
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Using the rifle/target analogy, a rifle that produces a 6" group centered around a bullseye is considered far less accurate and precise than a rifle that produces a 1" group that is 7" off center. In the first, you have no idea where each shot lands and therefore cannot predict where the next shot will go outside of a 6" radius. At 100yds, you would say that rifle is accurate to 6 minutes of angle.
The second example would produce 1 minute of angle accuracy and you can predictably know where the next shot will land so you can adjust/calibrate reliably.