In scientific experiments, failing to control variables or using improper measurement techniques can introduce errors. Match each experimental scenario with the primary source of error or confounding variable it introduces.
- A student tests the effect of wind speed on soil evaporation rates by placing one container near an open window and another in a closed closet.Confounding variable due to ambient environmental factors (temperature and air circulation changes).
- To measure the rate of respiration in yeast, a student conducts trials using three different brands of sugar, each containing varying ratios of glucose and fructose.Confounding variable due to uncontrolled chemical composition of the nutrient source.
- A researcher monitors the temperature changes of an exothermic reaction using a digital probe that consistently records values below the actual temperature.Systematic measurement error that affects all data points by a constant offset.
- A study investigates how light intensity affects plant growth by using seedlings of different heights and initial health statuses across the experimental groups.Confounding variable due to biological variation and baseline differences in specimens.
Answer
The experimental scenarios match their corresponding sources of error as follows: testing wind speed in different locations matches ambient environmental confounding factors; yeast respiration trials with different sugar brands matches uncontrolled chemical composition; a miscalibrated temperature probe matches systematic measurement error; and using plants of varying initial sizes matches biological variation confounding factors.
The correct matches align each scenario with its primary experimental flaw. Changing the location of the soil containers introduces ambient temperature and humidity variations (environmental factors). Varying the chemical composition of the sugar introduces an uncontrolled reactant ratio (chemical composition). The consistently offset digital thermometer demonstrates a calibration issue (systematic error). Finally, selecting seedlings of different initial states introduces baseline variation in the experimental units (biological variation).
Step-by-Step Solution
Key Concept
Identifying sources of error and confounding variables is essential to establish clear cause-and-effect relationships and ensure validity in experimental designs.