Factors affecting power

Power refers to the ability of a study to detect a true effect or relationship between variables. The following factors can affect the power of a study:

1. Sample size: Increasing the sample size of a study can increase the power of the study. This is because a larger sample size increases the precision of the estimate and reduces the variability of the sample mean.

2. Variability of outcome: When the variability of the outcome is high, it can decrease the power of a study. This is because high variability makes it harder to detect a true effect or relationship between variables.

3. Effect size: A larger effect size, or the magnitude of the difference between the groups being compared, increases the power of a study. This is because a larger effect size results in a larger difference between the groups and makes it easier to detect a true effect.

4. Significance level (alpha): The significance level, denoted by α, is the probability of making a Type I error, which is rejecting the null hypothesis when it is true. Decreasing the significance level reduces the probability of making a Type I error, but it also decreases the power of the study. This is because a smaller significance level requires stronger evidence to reject the null hypothesis, which can make it harder to detect a true effect or relationship between variables.

Overall, researchers need to carefully consider these factors when planning and designing a study to ensure that they have sufficient power to detect a true effect or relationship between variables. They may need to balance the trade-offs between sample size, variability of the outcome, effect size, and significance level to optimize the power of the study.

Resources:

1. How can we define the Power of Research study? | ResearchGate 

2. Statistical Power: What it is, How to Calculate it - Statistics How To 

3. An introduction to power and sample size estimation | Emergency Medicine Journal (bmj.com) 

4. Statistical Power and Why It Matters | A Simple Introduction (scribbr.com) 

5. What Is Power? | Statistics Teacher 

6. Factors Determining the Power of a Statistical Test for the Difference between Means and Proportions (sapub.org) 

7. 13.5: Factors Affecting Power - Statistics LibreTexts