An apparatus for determining candidate causes of a user experience degradation includes a data collection agent to collect inventory data associated with a managed computer system, a change recording system to process the inventory data and determine any changes and to record change records including time-stamps, an alert detection system to detect alerts (alarms and sensors) including time-duration information and storing alert records, an analysis module to select alert records based on whether the alert, using the time-duration information, occurred in a predetermined lookback period, and identify, for each selected alert records, corresponding change records that precede in time the selected alert records. A user reporting interface outputs the identified change records as the candidate causes. A plurality of managed computers includes condensing agents to transmit respective alert and change records to a master computer system for correlation analysis, and outputting candidate causes based upon the analysis.