An experiment is a systematic approach to prove or disprove a hypothesis and uncover new knowledge. Statistics is often used to interpret the results of an experiment. Consider an experiment to determine the relationship between mobile phone usage and sleep quality among college students. These students, referred to as subjects, are divided into two groups. One is experimental, while the other is a control group. Only the experimental group is allowed to use mobile phones thirty minutes before bedtime, while the control group acts as the standard of comparison. Researchers then record the number of hours of sleep and sleep latency or variables – the characteristics of subjects that are examined, measured, and interpreted. Variables are of two types: dependent and independent. Mobile phone usage is an independent variable controlled by researchers, and sleep hours and sleep latency are dependent variables that are measured and recorded. Finally, hypothesis testing is used to infer whether the observed changes in sleep quality in the experimental group over the control group are statistically significant.