# What is a variable (independent, controlled, dependent) and what is data? What is a description of accuracy, reliability, and validity?

A variable is an item, trait, or other factor within a scientific experiment that can change in quantity. In order to determine what causes the results of an experiment, only one variable should be changed at a time.

An independent variable is the variable whose quantity is regulated by the scientist. Therefore, the term “manipulated variable” can be used interchangeably with the term independent variable. The value of an independent variable determines the value of the other variables within the experiment.

The dependent variable is the variable that is measured by the scientist within a scientific variable. Thus, the dependent variable results in the data collected by the scientist. This can easily be remembered because “dependent variable” and “data” both start with the letter “d”. The value of the dependent variable depends on the value of the independent variable, hence its name. For this reason, the term “responding variable” is a synonym to the term dependent variable.

A controlled variable is any factor that is kept the same amongst all groups within a scientific experiment. Controls are used as constants so that scientists can easily determine what variable is responsible for a change.

The accuracy of an experiment is how close a data point is to the actual value of a known standard. Thus, accuracy can be thought of as the nearness of a data point to the bullseye of a dart board.

Accuracy can be compared to precision. Precision is the nearness of multiple data points to one another. Data is considered precise if the data points are clumped together, even if the clump of data points is not near a standard known value.

Reliability of a scientific experiment speaks to the consistency of the scientific tools used and, thus, the data produced. Reliable data is consistent. If an experiment is reliable, many scientists should be able to repeat the same procedures and obtain the same results.

In science, validity refers to whether or not an argument, conclusion, measurement, or test relates to real-world applications. Validity refers to how well an experiment truly represents it claims.