Prob-5 The lighting department of a city has installed 2000 electric lamps with an average life of 10,000 h and a standard deviation of 500 h. After what period of lighting hours would we expect 65.54% of the lamps to fail? Assume life of lamps are normally distributed. Sol: 50% 65,54%

A First Course in Probability (10th Edition)
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Chapter1: Combinatorial Analysis
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Prob-5
The lighting department of a city has installed 2000 electric lamps with an average life of 10,000 h and a standard deviation of 500 h.
After what period of lighting hours would we expect 65.54% of the lamps to fail? Assume life of lamps are normally distributed.
Sol:
50% 65,54%
Transcribed Image Text:Prob-5 The lighting department of a city has installed 2000 electric lamps with an average life of 10,000 h and a standard deviation of 500 h. After what period of lighting hours would we expect 65.54% of the lamps to fail? Assume life of lamps are normally distributed. Sol: 50% 65,54%
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