A scientist wants to determine the best light wavelength for growing plants. He grows plants in four test groups as shown in the table below. What, if anything, was wrong with the experiment.

Question

Group Light Wavelength CO2 Level Light Intensity
A (10 Plants) 400 nm 400 ppm 30%
B (10 Plants) 500 nm 700 ppm 80%
C (10 Plants) 600 nm 600 ppm 50%
D (10 Plants) 700 nm 200 ppm 80%

A. He should only grow one type of plant in each group.
B. He should only change the wavelength of light for each group.\
C. He should add a control group with a CO2 level of zero ppm and a light intensity of zero percent.
D. There is nothing wrong with the experiment.

Answer 1

The primary issue with the experiment is that there are multiple variables being changed between the test groups, namely the light wavelength, CO2 level, and light intensity. This makes it difficult to determine the specific effect of the light wavelength on plant growth, as changes in CO2 level and light intensity could also impact the outcomes.

Therefore, the best answer is:

B. He should only change the wavelength of light for each group.

By controlling for CO2 levels and light intensity, the scientist would be better able to isolate the effects of the different wavelengths of light on plant growth.