Sam’s Long Life 75-watt light bulbs are designed to have a life of 1,130 hours with tolerances of ±200 hours. The process that makes light bulbs has a mean of 1,010 hours, with a standard deviation of 54 hours. Compute the process capability ratio and the process.

Life of bulb = 1130 ± 200 hours

Lower specification level (LSL) = 1130 - 200

Lower specification level (LSL) = 930 hours

Upper specification level (USL) = 1130 + 200

Upper specification level (USL) = 1330 hours

S.D. of the process (σ) = 54 hours

Process mean (µ) = 1010 hours

Process capability = (USL – LSL)/6σ

Process capability = (1330 - 930)/(6*54)

Process capability =   400/324

Process capability = 1.2346

Process capability index = Minimum [(USL – µ)/3σ, (µ – LSL)/3σ]

= Minimum [(1330 - 1010)/(3*54), (1010 - 930)/(3*54)]

= Minimum [320/162], (80/162)

= Minimum[1.98, 0.49]

Process capability index = 0.429. The process capability > 1. Conclusion is that the process is capable.

Also, Process capability index =1.98. The process capability index < 1 and mean is towards lower specification limit, the bulbs produced will be of shorter life.

Process capability = 1.2346 (>1) indicates the process is capable, Process Capability = 0.49 (<1) indicates that shorter lived bulbs will be generated.

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the first successful, urban blues recording, selling more than 75,000 copies, was made in year 1920.

mamie smith recorded the first commercially successful example of the urban blues,   with the recording of “crazy blues”."crazy blues" was recorded on august 10, 1920, in new york city. within a month of the release of “crazy blues” it had sold 75,000 copies.