All of the reported data are simple, straight forward and self-explanatory statistical
parameters except the adjusted score which is the most important
Adjusted score, in a nutshell, is the estimated true portion of correct response
in terms of percentage. For example, an adjusted score of 80 means it is estimated
that 80% of the time the testee truly knows the correct color and the rest (20%)
of the time he just guesses. Since there are three choices, a completely color blind
person can get 1/3 of his responses right by randomly picking the choices. Therefore
correct portion of 33% is translated to an adjusted score of 0.
It is possible to have negative adjusted score. This means the testee's color vision
is even worse than complete color blindness. In other words, the wrong colors are
more likely to be picked than the correct ones. In reality, the negative adjusted
score is usually a result of statistical variation, especially of small sample numbers.
The design of this test, due to its uniform image pattern, uniform background and
random brightness, does not allow any inherent negative adjusted scores.
The protanopia (red-blind, missing long-wavelength photopigment) and deuteranopia
(green-blind, missing middle-wavelength photopigment) tests are almost the
same because the long (red) wavelength photopigment's spectral sensitivity is very
close to that of middle (green) wavelength photopigment. In other words, protanopes
and deuteranopes will probably test positive on both tests.