K
Kleeve
Does anyone know how is table for x-bar & R ctrl chart derived?
Well the problem is, i try to calculate the ctrl limit:UCL and LCL. Thru' understanding the limit are +/-3sigma thus i obtain the sigma value,then applied x_bar+/-3sigma to cal the ctrl limit.
But had no idea why the result varies from using the formula (x_bar+/-A2R_bar)? Very much greater... ...
Well the problem is, i try to calculate the ctrl limit:UCL and LCL. Thru' understanding the limit are +/-3sigma thus i obtain the sigma value,then applied x_bar+/-3sigma to cal the ctrl limit.
But had no idea why the result varies from using the formula (x_bar+/-A2R_bar)? Very much greater... ...