Thread: Good old Plop shot

The theory is that the population of all possible shots has a mean value and each shot has a random deviation from that location.

You try to estimate the location of that mean point of impact from a sample of shots fired on paper. At the same time you are estimating the size of the typical deviation (often we talk about group diameter but its mathematically easier to handle the standard deviation which is the root mean square deviation).

Now, the more shots you fire, the closer the observed sample's mean point of impact is to the theoretical population mean point of impact. You also get more information on the group size.
Groups of 1 shot each are pretty random. Groups of 3 shots are better and usually good enough to sight in with. Sometimes you'll get 3 consecutive shots all on the same side but mostly the mpi will be inside the triangle. Groups of 5 shots will almost always contain the true population MPI within them and you are starting to get an idea how good your grouping is.
So, if someone tries to sight in with 1 or 2 shot groups, they don't know the mpi and they don't know the amount of deviation, so the underlying population mpi will have a lot of randomness compared to where they see the shot fall.