Question

In an experiment to test the hypothesis that added phosphate will cause marigolds to produce more blooms, the experimenter has two groups of pots planted with marigold seeds. One group gets watered with phosphate added to the water, while the other group gets watered with no phosphate. Both groups get the same amount of water and light.
Which is a controlled variable in this experiment?
A. number of pots
B. amount of water
C. amount of phosphate
D. amount of blooms on a plant

Answer 1

C. Amount of phosphate
I am not really sure, but I know that a controlled group is when nothing is changed to that group, so I am thinking that the amount of phosphate is the controlled variable because one groups gets some while the other does not.

Answer 2

Answer: B. amount of water.

Explanation: Controlled variables are those that remain constant in an experiment in order to avoid misconclusion about the relation between the dependent and independent variables.

Dependent variables are those that rely on other variables and independent variables are the ones that the experimenter controls.

In this case dependent variable is the production of blooms because depends on how much phosphate is added, so independent variable is the amount of phosphate.

Control variable is amount of water because it affects the growth and production of plants but when the experimenter use the same amount in both trials is standarizing the effect and making non-relevant to the study.