- The probability of saying or concluding that a study found no difference between groups when in reality there is a difference.
- This is also known as the chance of making a type II error or false negative rate.
- β ("Beta") is an important part of power, which is defined as being 1 - β.
- Most clinicians accept a power of 0.8 (or 80%), which means β has to be 0.2 (or 20%)
- Reducing β will decrease the chance of making a type I error and at the same time increase the power of the study.
- Note: As β is decreased, the sample size will increase in order to find a difference if one exists. This will clearly add to the cost and time to complete a study.
What is Beta (β)?