An investigator wants to identify potential confounding variables and sources of error in various scientific investigations. Match each experimental design setup on the left with the corresponding source of error or confounding factor on the right.
- To compare bean plant growth in different soils, pots with soil A are placed in a sunny room, and pots with soil B are placed in a shaded room.Uncontrolled light exposure, which can independently influence photosynthesis and plant growth rates.
- To compare the evaporation rates of three liquids, open beakers of equal volume are placed on separate windowsills receiving different amounts of direct sunlight.Varying thermal energy from sunlight, which alters the rate of evaporation independently of the liquid type.
- To study the effect of temperature on a chemical reaction, reactions at different temperatures are stirred at different speeds on different hot plates.Differing rates of reactant collision and mixing due to variable stirring speeds, which can affect reaction rate.
- To test how exercise intensity affects heart rate, participants of different ages are assigned to different exercise groups.Baseline cardiovascular differences due to age, which can confound the relationship between exercise intensity and heart rate.
Answer
Bean plant growth in different soils matches with uncontrolled light exposure. Evaporation rates of different liquids matches with varying thermal energy from sunlight. Temperature effect on chemical reaction matches with differing rates of reactant collision due to variable stirring speeds. Exercise intensity effect on heart rate matches with baseline cardiovascular differences due to age.
Each setup is correctly matched to the uncontrolled variable that systematically co-varies with the independent variable, thereby obscuring the true relationship between the independent and dependent variables.
Step-by-Step Solution
Key Concept
Identifying confounding variables and uncontrolled factors in experimental designs
Estimated Time:1m 30s