# Types of variables

## Many types of variables are used to answer research questions

There are several types of variables that can be used in research. First and foremost, variables are chosen to answer research questions.

The

The

**mnemonic (**__PICO__**population**,**intervention**,**comparator**, and**outcome**) identifies important parts of clinical research questions and also helps researchers to think about what variables to choose to answer their research questions.**Click**on a button below to continue.### Variables

Demographic variables are collected so that samples can be described and so that inferences can be made to other populations as needed.

An independent variable is what a researcher manipulates to better understand its association with a dependent variable.

When a researcher wants to "control" for a variable, this means that they want to hold that variable constant to see if it affects the association between independent and dependent variables. The way to do this statistically is to put all variables of interest into a

**.**__simultaneous regression model__A dependent variable is what a researcher measures for to establish an association with an independent variable.

Predictor variables are the same as independent variables above. This terminology is often used in applied empirical and clinical settings. A predictor variable is hypothesized to have some sort of association with an outcome variable.

Confounding variables adjust the values of a dependent or outcome variable that is associated with an independent variable.

Outcome variables are the same as dependent variables above. Outcomes are always a central focus in applied empirical and clinical settings. The outcome variable should be measured at the current "gold standard" that exists.

## Hire A Statistician - Statistical Consulting for Students

**DO YOU NEED TO HIRE A STATISTICIAN?**

Eric Heidel, Ph.D.** **will provide the following statistical consulting services for undergraduate and graduate students at $75/hour. Secure checkout is available with Stripe, Venmo, Zelle, or PayPal.

- Statistical Analysis
- Research Design
- Sample Size Calculations
- Diagnostic Testing and Epidemiological Calculations
- Survey Design and Psychometrics