Question

Mario performed an experiment to determine if photosynthesis was affected by the amount of light that a plant received. The data from his experiment are shown in the table below.


Amount of light
(hours)

Number of plants
Average volume of oxygen produced (mL)
1
4
0.50
6
4
2.0
10
4
5.0

What could he have done to increase the validity of his data?
Reduce the number of plants.
Remove the 1 hour group.
Add a 0 hours control.
Measure the oxygen in liters.

Answer 1

Add a 0 hours control.

A zero‑light control gives a baseline for oxygen production with no light, so you can better attribute changes to the amount of light (increasing the experiment's validity).