A student group is designing various laboratory investigations. During their planning phase, they identify potential sources of error and confounding variables in their experimental setups. Match each described experimental procedure with the primary source of error or confounding variable that threatens its validity.
- Testing the effect of temperature on the rate of yeast respiration by placing the trials in a dark incubator and the trials on a brightly lit window sill.Introduction of light exposure as a confounding variable that may independently stimulate yeast activity or alter temperature uniformity.
- Comparing the transpirational water loss of two plant species by planting Species in porous clay pots and Species in non-porous plastic pots, while maintaining identical soil volume and watering schedules.Systematic difference in the pot material's permeability and moisture retention properties, which alters water loss independently of transpiration.
- Determining how affects enzyme activity by using a different chemical buffer system for each level, where some buffer salts can independently bind to and inhibit the enzyme's active site.Chemical interference from the buffer components themselves, which alters enzyme activity independently of hydrogen ion concentration ().
- Investigating the impact of wind speed on soil evaporation rates by conducting trials at high wind speeds in the morning and trials at zero wind speed at night in a greenhouse where the ambient relative humidity fluctuates daily.Uncontrolled fluctuation in ambient humidity over time, which independently alters the rate of evaporation regardless of wind speed.
Answer
Testing yeast respiration temperature effects matches with light exposure confounding; comparing plant transpiration in clay vs. plastic pots matches with container permeability differences; determining pH effects on enzymes using different buffers matches with chemical interference from buffer salts; investigating wind speed effects at different times of day matches with fluctuating ambient humidity.
Each experimental procedure is correctly matched to its confounding variable: testing yeast at different temperatures under different light conditions introduces light as an uncontrolled variable; using different pot materials (clay vs. plastic) introduces container permeability as a confounder; using different buffer compounds introduces chemical interference; and conducting evaporation trials at different times of day introduces fluctuating relative humidity as an uncontrolled factor.
Step-by-Step Solution
Key Concept
Identifying uncontrolled variables and confounding factors that prevent researchers from drawing valid conclusions about the relationship between the independent and dependent variables.