Analyzing measurement results of a target system. Data samples are analysed using an anomaly detection model to form an initial time series (401) of anomaly detection scores, wherein the data samples comprise measurement results of the target system. The initial time series (401) of anomaly detection scores is decomposed into a trend component (402), a seasonal component (403), and a remainder component (404), wherein the remainder component is determined by deducting the trend component and the seasonal component from the initial time series. At least the remainder component of the anomaly detection scores is output for the purpose of evaluating performance of the target system.