of exceeding the upper control limit
. (Here X indicates the random count for the week.) On the other hand, if the mean is just slightly higher, say [[mu].sub.t] = 6.5, then the upper control limit
is 14.63, leaving a probability of
This was tried both ways, and the upper control limit
tended to be quite wide when the limits were based on the [chi square] limits.
The points are erratic; two points are significantly above the upper control limits
, and a few points are on or below the lower control limits.
For example, the lab manager noticed the control chart for ML had peaked above the upper control limit
. This told him something had changed, and that this change was adversely affecting the product.
Therefore, in case I, the control chart for this case also has an upper control limit
equal to an appropriate percentile of chi-square distribution.
2) Calculate the upper control limit
, UCL and the lower control limit, LCL of the arithmetic average surface roughness [R.sub.a] and the surface roughness [R.sub.z], which are used in the I-MR charts.
t + 1] = the upper control limit
in time period t + 1; [LCL.sub.t + 1] = the lower control limit in time period t + 1; [z.sub.t] = the center line (Eq.
The probability upper control limit
is compared with the 3-sigma upper control limit
At Point 3 on the chart, the deviation of the dimension was out of the established parameter (above the upper control limit
(UCL) for the dimension).
Then, to keep [Alpha] unchanged, we try to relax the upper control limit
at the same time.
1, they are marked [UCL.sub.X], [LCL.sub.X] for upper control limit
and lower control limit for X and [UCL.sub.R], for upper control limit
They are added to make both the probabilities below the lower control limit -3 and above the upper control limit
3 closer to (0.27 per cent)/2 = 0.135 per cent.