What is considered an acceptable attrition rate for a study?

An attrition rate is the percentage of participants who drop out of a study before it is completed. An acceptable attrition rate can vary depending on the context of the research, but generally, lower rates are preferred as they indicate that the study is retaining its participants effectively.

An attrition rate of less than 5% is often viewed as excellent and suggests that the study has been successful in maintaining participant engagement and minimizing dropouts, which helps to ensure that the study results are reliable and valid. When the attrition rate is low, it reduces the risk of bias and strengthens the internal validity of the study, making it easier to draw conclusions from the data collected.

Higher attrition rates, such as those around 15-20% or greater than 20%, can raise concerns about the representativeness of the sample and can result in potential biases in the findings. While some studies may still produce valid results with higher attrition rates, lower rates are generally more desirable as they indicate better participant retention and, consequently, more robust results.