Question

variables in scientific experiments
a variable is any factor that can be changed, measured, or controlled in a scientific experiment. understanding the different types of variables is crucial for designing and interpreting experiments. there are three main types of variables: manipulated (independent), responding (dependent), and controlled.
key definitions

• manipulated variable (independent variable): this is the variable that the scientist intentionally changes or manipulates during the experiment. its the “cause” in a cause - and - effect relationship. think of it as the factor you are testing.
• responding variable (dependent variable): this is the variable that changes in response to the manipulated variable. its the “effect” in the cause - and - effect relationship and is the factor you measure or observe.
• controlled variable (constant): these are all the factors that are kept the same throughout the entire experiment. keeping them constant ensures that any change in the responding variable is truly due to the manipulated variable and not something else.

practice scenarios
for each scenario or lab experiment below, identify the manipulated, responding, and controlled variables.

1. scenario: a scientist wants to know if the amount of water a plant receives affects its growth. she gives three identical plants different amounts of water (200 ml, 400 ml, and 600 ml) each day for two weeks and measures their height.

manipulated variable
responding variable
controlled variables

Explanation:

Step1: Identify the manipulated variable

The scientist changes the amount of water given to the plants. So the manipulated variable is the amount of water (200 mL, 400 mL, 600 mL).

Step2: Identify the responding variable

The scientist measures the height of the plants. So the responding variable is the height of the plants.

Step3: Identify the controlled variables

The plants are identical, the time - period is two weeks for all plants. So the controlled variables are the type of plant, the time of the experiment (two weeks).

Answer:

Manipulated Variable: Amount of water (200 mL, 400 mL, 600 mL)
Responding Variable: Height of the plants
Controlled Variables: Type of plant, time of the experiment (two weeks)