I know that it’s needed of at leat 20 batches to calculate the ctrl limits.

I cannot wait to reach the 20 timepoints.

I know that there is the possibility to apply the 75%delta approach to calculate the ctrl limits. It’s can be applied in presence of the specification limits for the following cases:

- dataset not normal distributed;

-...

Calculation control limits]]>

thanx in advance]]>

Currently we have implemented SPC for past 2 years with more than 100 of machines in our production lines. Most of the parameters have only either upper or lower spec limit, as a result, our control limits are turn on for only on sided limit, either LCL or UCL.

One of the problem is, we have some parameters with only lower spec limit and lower control limit, (ex two components bonding force), that mean, we expect the data...

S chart Upper control limit]]>

Thank you very much.]]>

2- no of total defects / no of total production * 1000000

3- ( no of total defects / no of total production for each process * no of processes ) * 1000000]]>

1 material - 16 samples are measured and CP , CPK are calculated as well but below formula used for yield calculation :

Formula : Normsdist(3*CPK) or Normsdist(3*CPK)+Normsdist(6*CP-3*CPK)-1.]]>

I have a continuous production every day and the quantities varies between 1000-1500 per day. Every part have its own measurement result as the shown below

Part 1 - 25.06

Part 2 - 24.07

Part 3 - 25.85

.

.

Part 1120 - 25.65

Part 1 - 24.09

Part 2 - 24.07

Part 3 - 25.35

.

.

Part 990 - 25.45

and we have our own UCL LCL limits as 25.9 - 24.0

Every chart that i've seen had multiple observation per each part. I only have one...

haven't considered which chart should i use]]>

Thanks]]>

The variable data we collect is normally distributed.

- The skew and kurtosis are with +/-2.
- The mean equals the median.
- The χ2...

Cpk >2.5, data is normal, but SPC is totally out of control]]>

Our SPC...

SPC question for batch style processing]]>

Numbers of people on a waiting list by month. If jan there were 100, feb 120, March 135 etc. The numbers are not new patients, they are the total numbers on the waiting list, therefore marchs number of 135 is dependent on febs number.

In this case is Spc and ucl/lcl relevant?]]>

So, based on my knowledge I used P chart, the problem is that the distribution is not binomial, and the distribution is normal. So Is it possible to use another tools like X-bar or not? Because, it is better for us to have Cpk, too.

Looking...

My data is attribute but the distribution is normal]]>

Cp and Cpk for little groups]]>

I'm trying to do SPC in consumer electronic industry and we make AC-AC converters, AC-DC converters. I was wondering what factors would be best suitable for monitoring the process? For example, Output Voltage or Ripple Voltage.

Also how would these processes hint me about the process going out of control. Would appreciate any help in this regard.]]>

Another scenario is, there are difference found in Cpk values from different source of data. When the raw data is extracted for a particular process, the Cpk is showing 99.99. However when refer back to the chart, the chart is displaying a...

Cpk 99.99 on charts & raw data]]>