<p>A monitoring system analyzes the cause of an event that occurs in any of a plurality of node devices. The monitoring system stores a plurality of rules that indicate the relationships between one or more conditional events related to any of the plurality of node devices and conclusions. The monitoring system identifies a first conclusion associated with a detected conditional event on the basis of the rules, determines whether the monitoring system can detect each of one or more conditional events among a plurality of conditional events, and calculates a first index value indicating the likelihood of the first conclusion being the cause, on the basis of whether the one or more conditional events associated with the first conclusion are detected and on the basis of the result of whether the monitoring system can detect each of the one or more conditional events.</p>
