A student designed an experiment to investigate how the concentration of fertilizer affects the growth of *Arabidopsis thaliana* plants. The student prepared four pots, each containing five seedlings. Pot 1 was watered with a 0% fertilizer solution (distilled water), Pot 2 with a 1% solution, Pot 3 with a 5% solution, and Pot 4 with a 10% solution. Pots 1 and 2 were placed on a sunny windowsill, while Pots 3 and 4 were placed on a shaded shelf in the same room. All pots received the same volume of liquid daily. After three weeks, the average height of the plants in each pot was measured. Which of the following identifies the primary confounding variable in this experimental design?
- The different locations of the pots, which exposed the plants to varying levels of sunlightCevap
- BThe different concentrations of fertilizer solution applied to each pot
- CThe use of Pot 1 as a control group receiving 0% fertilizer solution
- DThe number of seedlings planted in each pot
Cevap
The different locations of the pots, which exposed the plants to varying levels of sunlight
The correct answer is the option identifying the different locations of the pots. In a well-designed experiment, only the independent variable (fertilizer concentration) should vary between groups. Because the pots were placed in different locations (sunny windowsill vs. shaded shelf), the plants received different amounts of sunlight. Sunlight is a critical factor for plant growth, so this difference acts as a confounding variable, preventing the student from determining whether the fertilizer or the light levels caused the differences in growth.
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Anahtar Kavram
A confounding variable is an uncontrolled factor that varies along with the independent variable, making it impossible to isolate the cause of any observed changes in the dependent variable.
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