A medical researcher wants to determine whether exercising can lower blood pressure. At a health fair, he measures the blood pressure of 100 individuals, and interviews them about their exercise habits. He divides the individuals into two categories: those whose typical level of exercise is low, and those whose level of exercise is high.
a. Is this a controlled experiment or an observational study?
b. The subjects in the low exercise group had considerably higher blood pressure, on the average, than subjects in the high exercise group. The researcher concludes that exercise decreases blood pressure. Is this conclusion well-justified? Explain.
(a) An observational study
(b) It is not well-justified. Because the study is observational, there could be differences between the groups other than the level of exercise. These other differences (confounders) could cause the difference in blood pressure.
You might also like to view...
Trail is the distance between the center of the front axle and the center of gravity.
Answer the following statement true (T) or false (F)
When using hydrochloric acid in an etch test, the proportion of concentrated hydrochloric acid to water is ____.
A. one to one B. two to one C. nine to one D. one to nine
Because of its often high-protein content, alfalfa is a poor choice of hay for the horse
A. True B. False
Two technicians are discussing climate control systems. Technician A says climate control can be a straight heater system or a combination of heat and air conditioning. Technician B says the heater system depends on the engine and its thermostat for operation. Who is correct?
A. A only B. B only C. Both A and B D. Neither A nor B