In an experiment to test the effect of sugar concentration on yeast fermentation, different sugar concentrations were used while the type of yeast and temperature were kept constant. The amount of carbon dioxide produced was measured. What was the independent variable?
- Sugar concentration (correct answer)
- Type of yeast
- Temperature
- Amount of carbon dioxide
Explanation: The independent variable is sugar concentration (what was varied across different levels), the dependent variable is amount of carbon dioxide produced (what was measured), and controlled variables include type of yeast and temperature (kept constant). The independent variable is the factor deliberately manipulated by the experimenter to test its effects. Choice A correctly identifies sugar concentration as the independent variable since this was intentionally varied to study its effect on fermentation.