An unmanned monitoring system uses high-tech video equipment and microprocessors to detect intruders. A prototype system has been developed and is in use outdoors at a weapons munitions plant. The system is designed to detect intruders with a probability of .90. However, the design engineers expect this probability to vary with weather condition. The system automatically records the weather condition each time an intruder is detected. Based on a series of controlled tests, in which an intruder was released at the plant under various weather conditions, the following information is available: Given the intruder was, in fact, detected by the system, the weather was: * Clear 75% of the time, * Cloudy 20% of the time, and * Raining 5% of the time. When the system failed to detect the intruder: * 60% of the days were clear, * 30% of the days were cloudy, and * 10% of the days were rainy.