Question

in a controlled scientific experiment, a scientist
a. alters the test variable (independent variable) and observes the effects on the outcome variable (dependent variable).

b. alters one outcome variable (dependent variable) and observes the effects on other outcome variable (dependent variables).

c. alters one test variable (independent variable) and observes the effects on other test variables (independent variables).

d. alters the outcome variable (dependent variable) and observes the effects on the test variable (independent variable).

Explanation:

In a controlled scientific experiment, the independent variable (test variable) is manipulated by the experimenter, and the dependent variable (outcome variable) is what is observed to see the effect of the independent variable. Option A correctly describes this: the scientist alters the independent variable and observes the effect on the dependent variable. Option B is incorrect because the dependent variable is not altered; it is the outcome. Option C is incorrect as we observe the effect on the dependent variable, not other independent variables. Option D has the relationship reversed; the independent variable is altered to see its effect on the dependent variable, not the other way around.

Answer:

A. alters the test variable (independent variable) and observes the effects on the outcome variable (dependent variable).