An experimental design is one that uses the scientific method in order to understand a causal phenomenon. The experimental method consists of forming a causal hypothesis, implementing a variable in an experimental group, having a control group, collecting data, and statistically analyzing the data in order to determine if there is a significant difference in the results between the two groups. One hallmark of the experimental design is that of random assignment. This means that each subject has an equal chance to be assigned to the experimental group and the control group. This ensures equivalency between the groups, thereby having confidence that, if a difference were found between the experimental and control group, it would be due to the experimental variable.