Answer Posted / arul
1) Sigma means the standard deviation of the data obtained.
Eg: Turning a shaft for 50mm will never give 50.0000000mm.
There will be variation in the machined dimension. For
measuring the variations v use the parameter standars
deviation. RMS (root mean square) of the deviations from
the mean vaue is standard devation.
2) All the manufacturing & m/c dimensions can be
approximated to lie in a normal curve (bell shaped curve
symm about mean and showing max. freq at mean.)
3) Kindly refer to standard normal curve and its values.
U ll surely come to know 6 sig is better than 3 sig
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