Cylindrical pins of diameter 15±0.020 mm are being produced

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Cylindrical pins of diameter 15±0.020 mm are being produced on a machine. Statistical quality control tests show a mean of 14.995 mm and standard deviation of 0.004 mm. The process capability index Cp is

1. 0.833
2. 1.667
3. 3.333
4. 3.750

Correct Option: B

Diameter of cylindrical Pin = 15 ±.020
Upper Specification limit = 15 + 0.02 = 15.02 mm
Lower Specification limit = 15 – 0.02 = 14.98 mm
Standard deviation (σ) = 0.004 mm
Process capability Index

C_p =	USL - LSL	=	15.02 - 14.98	= 1.667.
	6σ		6 × 0.004