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 scientific experiment, for results to be valid, variables that can affect the outcome (other than the independent variable being tested) must be controlled. Here, the student did not control all such variables, like watering method differences (hand - watering vs. sprinklers), which could impact plant growth instead of just the talking variable.

Answer:

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