Which technique for gathering data (sampling, experiment, simulation, or census) was used in the following studies? a

Which technique for gathering data (sampling, experiment, simulation, or census) was used in the following studies?

a. An analysis of a sample of 31,000 patients from New York hospitals suggests that the poor and the elderly sue for malpractice at one-fifth the rate of wealthier patients. (Journal of the American Medical Association).

b. The effects of wind shear on airplanes during both landing and takeoff were studied by using complex computer programs that mimic actual flight.

c. A study of all-league football scores attained through touchdowns and field goals was conducted by the National Football League to determine whether field goals account for more scoring events than touchdowns (USA Today).

d. An Australian study included 588 men and women who already had some precancerous skin lesions. Half got skin cream containing a sunscreen with a sun protection factor of 17; half got an inactive cream. After 7 months, those using the sunscreen with sun protection had fewer precancerous skin lesions (New England Journal of Medicine).