Measuring performance through audit projects in orthopaedics - how do you know your performance is up to standard?

Clinical audit is an activity that involves all health care professionals and is used to assess the quality of service provision by comparing performance against some agreed standard or target. However, in order to decide if performance is at (or near) the standard or target, it is necessary to analyse the data with more than just descriptive statistics. This paper introduces readers to the use of decision making (or inferential statistics) as a valuable tool in the measurement of performance and in so doing also discusses issues about the size of the sample from which audit data is collected.