Question

a student conducted an experiment to test whether talking to plants would help them to grow faster. he set up the following two groups. group 1: spoken to and hand watered. group 2: not spoken to and watered with sprinklers. after three weeks, the plants in group 1 showed much more growth than those in group 2. based on the results of this experiment, which is the best conclusion? they are valid because the student ran a controlled experiment. they are not valid because the student did not control all the variables that can affect plant growth. they are valid because the dependent variable caused a change in the independent variable. they are not valid because the time frame to grow a plant is too short.

Explanation:

In a valid experiment, all variables except the independent variable (talking to plants in this case) should be controlled. Here, different watering methods (hand - watering vs sprinkler - watering) are an uncontrolled variable that can affect plant growth. So the experiment is not valid.

Answer:

They are not valid because the student did not control all the variables that can affect plant growth.