Final answer:
The data collection method described is a controlled experiment because the researcher is deliberately manipulating an independent variable (light) to observe its effect on plant growth.
Step-by-step explanation:
The data collection method described by the student involves a researcher dividing 50 bean plants into two groups, with one group placed by a window and the other under artificial light, and then recording the plants' growth weekly. This scenario constitutes a controlled experiment because the researcher is directly manipulating the independent variable, which in this case is the type of light (natural vs. artificial) that the plants are exposed to. The researcher then observes the effect of this manipulation on the dependent variable, which is the growth of the bean plants.
In this situation, the researcher is randomly dividing 50 bean plants into two groups and putting one group by a window to receive natural light and the second group under artificial light. This is an example of a controlled experiment.