In many studies, multivariable statistical models are used to estimate an effect after controlling for a number of extraneous factors. For example, a statistical model might be used to estimate the effect of an intervention on 30-day mortality probabilities, adjusting for the severity of the patient s condition at the time of the intervention. Statistical models are also used for predicting outcomes, such as final diagnosis or in-hospital mortality. This section describes the uses, interpretation and limitations of statistical models.