What was the power behind Jim Crow?

“I can ride in first-class cars on the railroads and in the streets,” wrote journalist T. McCants Stewart. “I can stop in and drink a glass of soda and be more politely waited upon than in some parts of New England.” Perhaps Stewart’s comments don’t seem newsworthy. Consider that he was reporting from South Carolina in 1885 and he was black

Explanation:

answer:

d. because dr. laguardia selected a widely used measure, his study generalizes to has strong external validity. external validity has limited external validity. other applications of this measure.

the widely used measure that he applied to his experiment was the benton facial recognition test. it employed on to football players and as result, only players who suffered brain concussions did not pas this test. and although it has an external validity, it is limited because it isn't general to apply to other population.