A variable is something that researchers are studying in a research project or experiment. Every scientific experiment involves at least one independent variable and one dependent variable. Discover the difference between these two types of variables and review several examples of each type.
Independent vs. Dependent Variables
Well-designed research projects require different types of variables. But what's the difference between independent and dependent variables? Their definitions can help you see the differences.
- independent variable - the variable that the research changes (for example, the weight-control medication that a certain research group gets)
- dependent variable - the variable that the researcher is testing and measuring in relation to the independent variable (for example, how much weight the research group actually loses)
The researcher determines whether manipulating the independent variable leads to different outcomes regarding the dependent variable. Basically, the dependent variable depends on the independent variable (also known as a treatment variable).
Independent and Dependent Variables Examples
There are many independent and dependent variables examples in scientific experiments, as well as academic and applied research. You even use these variables in your daily life! For example, when you try out a new workout routine or diet (the independent variable), you measure how beneficial it was in your day (the dependent variable). Take a look at these independent and dependent variables examples in multiple disciplines.
Carb Loading and Endurance
An exercise physiologist wonders if carb loading (eating a lot of carbohydrates) the day before participating in endurance activities (such as triathlons or marathons) impacts performance.
- independent variable - quantity of carbohydrates consumed within a defined timeframe
- dependent variable - performance in an endurance activity
A scientist studies the impact of a drug on cancer. She administers the drug to a research group and a placebo to a control group.
- independent variable - administration of the drug (such as dosage or timing)
- dependent variable - the drug's impact on cancer
Rats and Affection
A scientist studies the impact of withholding affection from rats. One group receives a lot of affection, while the other receives none.
- independent variable - amount of affection
- dependent variable - reaction of the rats
A researcher explores whether people who already speak multiple languages learn new languages faster than people who only speak one language.
- independent variable - number of languages spoken
- dependent variable - amount of time to master a new language
Education and Earnings
A researcher wants to know if education level impacts how much a person earns in their job. She studies the amount of education a person has in their life to their current earnings.
- independent variable - highest level of educational attainment
- dependent variable - earnings (salary or wages)
National Origin and Net Worth
A social scientist wonders if there is an association between a person's national origin and their wealth, measured as net worth.
- independent variable - a person's country of origin
- dependent variable - a person's financial net worth
Time Spent Studying and Academic Success
An educational researcher explores whether there is a link between the amount of time someone spends studying and the grade they get in a particular class.
- independent variable - amount of time spent studying for a particular class
- dependent variable - grade in the class
Job Satisfaction and Pay
A human resources professional wonders if how much money a person earns can impact the extent to which an individual experiences job satisfaction.
- independent variable - compensation (salary or wages)
- dependent variable - job satisfaction
Sunlight and Plant Growth
A botanist wonders if the amount of direct sunlight a plant receives impacts how quickly it grows.
- independent variable - amount of direct sunlight plant receives
- dependent variable - speed of plant growth
Airline Travel and Influenza Infection
A medical researcher wonders if the amount of airline travel a person engages in impacts how likely they are to catch influenza during flu season.
- independent variable - amount of airline travel
- dependent variable - influenza infections
Chiropractic Treatments and Migraines
A scientific researcher wonders if regular chiropractic care decreases the frequency and/or severity of migraine headache episodes
- independent variable - how often chiropractic care is received
- dependent variables - frequency of migraine episodes; severity of migraine episodes
Socioeconomic Status and Number of Children
A social scientist explores if there is a link between socioeconomic status and the number of children someone has.
- independent variable - socioeconomic status
- dependent variable - number of children
News Viewership and Knowledge of Facts
A media studies researcher wonders if the amount of time a person spends watching television news contributes to how much factual information people know about current events.
- independent variable - amount of time a person watches TV news
- dependent variable - how much factual information a person knows about current events
Making Sense of Variables
Scientific research questions, experiments and statistical data analysis can get very complex. Learning how to recognize the difference between independent and dependent variables will provide you with a strong foundation before you start learning about other types of variables. To further expand your research skills, review some examples of research paper purpose statements.