ABSTRACT
A working knowledge of statistics is essential for any healthcare professional working within the sphere of orthopaedics. In well-designed studies, statisticians work in conjunction with orthopaedic surgeons from the outset, to maximize the methodological and statistical strength of a research study. All orthopaedic surgeons should have an awareness of the principles of study design, and be able to interpret the results of a study objectively. Plotting of data allows determination of central tendency and spread (or variability/variance). The familiar symmetrical bell-shaped curve of a normal (or Gaussian) distribution allows for the use of the mean as a measure of central tendency and is common throughout medicine. The easiest examples of skewed distributions concern age, i.e. positive skew, age at which anterior cruciate ligament (ACL) surgery occurs; negative skew, age at which total hip replacement (THR) surgery occurs. Errors may arise when accepting or rejecting the null hypothesis.
