Let’s say that you’re interested in buying some plants and you want to see what type of plant grows the fastest if you give each of them equal amounts of water. In this example, it’s fairly easy to define the independent and dependent variables. First, list the variables in this experiment and then identify those which are independent and those that are dependent. The variables are the type of plant and the height of each plant. Because the amount of water isn’t changing, it isn’t either option. Now, to determine which of the variables is independent, we must think about which variable is affected by the other variable. The type of plant isn’t affected by the height of each plant, so the plant’s type is the independent variable. This makes the height of the plants the dependent variable because the height does depend on the type of plant.

A school wants to discover whether or not the amount of sleep a student gets affects their test scores. The variables in this problem are the amount of sleep and the test scores. The test scores depend on the amount of sleep, so they are the dependent variable while the amount of sleep is the independent variable.

If you wanted to find out how tired you felt after certain amounts of caffeine, it would be fairly simple to determine which are the independent and dependent variables. Your tiredness would depend on how much caffeine you had, making your tiredness the dependent variable. The amount of caffeine is the independent variable.

Getting a bit more complex, think about a job that offers a variety of tasks. The amount you are paid is based on the quality of your work, but each task has a different starting wage. If you wanted to find out how much money you would earn, it would help to know the dependent and independent variables. The variables are the type of task, the starting wage, and the quality of work.

If a scientist wanted to discover whether or not moths were attracted to a certain level of brightness in lights, she could list out several variables. The first variable is the level of brightness. Then, maybe she wants to try it out on different species of moth. That’s another variable. Finally, we have the level of attraction. The only dependent variable is the level of attraction. The other variables aren’t being measured and aren’t changed by the other variables.

A person might wonder if heating water will help sugar dissolve faster. The variables in this problem are the temperature of the water, the amount of sugar that dissolves completely, type of sugar, and method of stirring. In an experiment like this, you would want to keep the stirring variable and type of sugar variable consistent. They are neither independent or dependent. The amount of dissolved sugar is what you would be measuring, and because it is the variable affected by the water temperature, it is considered the dependent variable.

To find an individual’s cost of living, you would need to consider variables such as salary, age, location, marital status, and expenses. Each of the listed variables is independent while the actual cost of living is dependent. The cost of living is what is being measured, and it is heavily affected by the other variables.

Picking out the independent and dependent variables can be done outside of singular studies and tests. This can be even more difficult than before because, in real life, there is no end to the number of variables. For example, the number of sales depends on variables such as customer demographics, weather, and store location. These are all independent variables. However, you could continue adding to that list with a million other potential variables, so it is important to remember the basic rules. If it is being measured and is affected by other variables, it is a dependent variable.