The power of a statistical test is a measure of a study’s ability to detect a statistically significant difference between the results of the intervention group and the control group in a randomized controlled trial. A difference is considered statistically significant when it is highly unlikely to have occurred by chance. A study’s power is partly determined by the size of the difference in scores between the groups, but it is also affected by how many people are included in the study and how much variation there is within each of the groups. For example, if there are too few people in the study, even a large difference may not produce a statistically significant result. [CIHR]