Friendship is Magic, and Magic is Heresy.
The only method of calculating this without population level data requires assuming your sample is unbiased and subbing in your sample standard deviation to calculate a standard error.They probably have a margin of error involved,
That assumption is entirely wrong.
but they have quite extensive market research at their disposal through Hasbro.
Not even Hasbro can (or will) field a full census of all players of 5e.