Question

Megan experimented with growing mold. She took 3 pieces of bread from the same loaf and placed each into a plastic sandwich bag. Before sealing the bag, she added 5 drops of water to each slice. Next, she placed one bag on her window sill, one in a dark cabinet, and one in a room away from sunlight. Megan concluded that the different amount of mold that grew on each slice was due to the amount of light it received. Is this a valid conclusion?

Responses

Yes, because the light was the manipulated variable
Yes, because the light was the manipulated variable

Yes, because the light was the controlled variable.
Yes, because the light was the controlled variable.

No, because the light could not have affected the growth
No, because the light could not have affected the growth

No, because the light should have been the same for each bread slice

Answer 1

No, the conclusion is not valid because Megan only varied the amount of light that the bread slices received and did not control for other variables that could have affected the growth of mold, such as temperature and humidity. Additionally, the experiment should have had a control group where a slice of bread was left without any water or placed in a bag but not exposed to any conditions, to serve as a baseline for comparison.