Asher notices mold on all twenty pea plants in his garden. He wonders what factors are contributing to the mold growth. He hypothesizes that he is giving the plants too much water, which is causing the mold to grow.Asher carries out an investigation in which he waters ten of the plants the same amount as before and gives the other ten plants half as much water per day. Each week, he photographs and records the number of leaves that contain mold. After a month, he observes his data and concludes that there has been little to no change in mold growth. What change to this experiment would be most effective in helping Asher continue to investigate what is causing mold growth?
Answer
A
He could change the dependent variable to “amount of shade” and set up shade umbrellas over ten of the plants.
B
He could change the independent variable to “amount of sunlight” and trim taller plants nearby so ten of the plants are no longer shaded.
C
He could add more controls so there is less chance that other factors are contributing to the mold growth.
D
He could change the timing of data collection so he is recording observations every two days for two full months.
Explanation
Reducing the water did not noticeably change mold growth, so Asher should investigate another possible cause while measuring mold the same way. Choice B tests whether sunlight affects mold by comparing plants with different amounts of shade. Trimming nearby plants changes sunlight exposure; keeping the other conditions the same helps make that comparison useful. Choice A changes the measured outcome instead of measuring mold growth.
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