The experimental variable
An important element that is defined in the metadata of each experiment is the "experimental variable".
The experimental variable is usually one or several of the sample attribute categories. It describes the factors that differ between the test and the control samples, which you are investigating (Figure 7).
Examples of common experimental variables are:
- growth condition
Figure 7 Examples of experimental variables.
At least one experimental variable must be specified for each experiment in ArrayExpress because it helps to identify the specific experimental conditions you are interested in. You will see how this is useful for retrieving precise search results in the next section.