In business and educational settings, computer presentations use liquid crystal display (LCD) projectors. The most common failure mode of these projectors is the failure of the lamp. Many manufacturers include the "expected" lamp life in their technical specification documents, and one manufacturer claims that users can expect 500 hours of projection time for each lamp used under "normal operating conditions". To test this claim, a large private university placed identical lamps in three projector models for a total of 10 projectors. The university staff recorded the number of projection hours when each lamp burned out