Color-blindness is any abnormality of the color vision system that causes a person to see colors differently than most people or to have difficulty distinguishing among certain colors (www.visionrx.xom).

Color-blindness is gender-based, with the majority of sufferers being males.

Roughly 8% of white males have some form of color-blindness, while the incidence among white females is only 1%.

A random sample of 20 white males and 40 white females was chosen.

Let X be the number of males (out of the 20) who are color-blind.

Let Y be the number of females (out of the 40) who are color-blind.

Let Z be the total number of color-blind individuals in the sample (males and females together).