How many independent

Generally, experiments are designed with one independent variable being manipulated at a time to clearly observe its effect on the dependent variable. However, there are situations where researchers may include two or more independent variables, especially in factorial designs, where the interaction between variables is also being studied.

Despite decades of political analysis focused on the two major parties, our research, along with others, confirms that as many as 51% of Americans now identify as independent. Partisanship has been in steady decline since Obama's re-election in 2012, and since then, independents have consistently been the largest political affiliation in America.

Note 1: In this listing, the term “independent state” refers to a people politically organized into a sovereign state with a definite territory recognized as independent by the US. Note 2: Geopolitical Entities, Names, and Codes (GENC) Standard two-letter and three-letter codes.

Each of these is a separate independent variable. To ensure the internal validity of an experiment, you should only change one independent variable at a time. What is differential attrition?

The main reason to restrict the number of independent variables is to maintain clarity. Each independent variable can introduce its own complexity and potential confounding factors, making it harder to determine the effect each variable has on the dependent variable.

In an experiment, you can technically have multiple independent variables, but it's important to limit them to avoid complications in your results. Generally, experiments are designed with one independent variable being manipulated at a time to clearly observe its effect on the dependent variable.