oyed is 10 per cent. This means that
10 per cent of hits are made. But it means another thing equally
important--it means that 90 per cent of misses are made. To what
are these misses due? Clearly they are due to errors made, not
necessarily by the man who fires the gun, but by all the people
concerned. If the correct sight-bar range were given to the gun,
and if the gun were correctly laid and the pointer pressed the
button at precisely the right instant, the shot would hit the target,
practically speaking. But, in actual practice, the range-finder
makes an error, the spotter makes an error, the plotting-room makes
an error, the sight-setter makes an error, and the gun-pointer
makes an error. The sum total of all of these errors results in
90 per cent of misses.

Suppose that by careful training these errors are reduced in the
relation of 9 to 8, so that instead of there being 90 per cent
of misses there are only 80 per cent. This does not seem a very
difficult thing for training to accomplish, but note the result: the
hits are increased from 10 per cent to 20 per cent. In other words,
by a decrease in errors in the relation of 9 to 8, the effective
skill and the hits are doubled.

Conversely, if the errors increased in the ratio of 9 to 10, the
misses would increase from 90 per cent to 100 per cent, and the
hits would be reduced from 10 per cent to 0.

Suppose now that the conditions are so very difficult that only
1 per cent of hits is made, or 99 per cent of misses, and that by
training the misses are reduced from 99 per cent to 98 per cent.
Clearly, by a decrease of errors of hardly more than 1 per cent
the effective skill and the hits are doubled.

Conversely, if the errors increased in the ratio of 99 to 100,
the misses would increase from 99 per cent to 100 per cent, and
the hits would be reduced from 1 per cent to 0.

But suppose that the conditions are so easy that 90 per cent of
hits are made and only 10 per cent of misses. Clearly, if the errors
were divided by 10, so that only 1 per cent of misses was made,
instead of 10 per cent, the number of hits would increase only
9 per cent, from 90 per cent to 99 per cent.

Of course, this is merely an arithmetical way of expressing the
ancient truths that skill becomes more and more important as the
difficulties of handling an instrument increase; and that, no matter
how effective an instrument may be when used with perfect skill,
the actual result obtained