1. A method of determining the root cause of service degradation in a network, the method comprising: determining a window of time; determining one or more abnormal Key Quality Indicators (KQIs) in the window; determining one or more abnormal Key Performance Indicators (KPIs) in the window; calculating a conditional probability that each of one or more KPIs is abnormal when a Key Quality Indicator (KQI) is normal; calculating a conditional probability that the each of one or more KPIs is abnormal when the KQI is abnormal; calculating a score for each KPI based upon a divergence of a Beta distribution for the conditional probability that each of one or more KPIs is abnormal when a KQI is normal, and a Beta distribution for the conditional probability that the each of one or more KPIs is abnormal when the KQI is abnormal; and generating a representative root-cause list based upon the score for each KPI.