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Apr 15, 2019 1:30 PM
(4062 views)

I got machine in lab for which I have set limits and I am trying to find out what is the probability of failing in the the future or if I'll get readings out of spec. First I used control chart builder and then did capability analysis and I got the following nonconformance table. Is this telling me that 2 out of 100 reading will be out of spec? What is expected within %?

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**Note:** You can change the preferences for stability assessment type in File > Preferences > Platforms > Process Capability. This changes the stability assessment type used through the Process Capability platform.

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Created:
Apr 15, 2019 7:01 PM
| Last Modified: Apr 15, 2019 7:02 PM
(4043 views)
| Posted in reply to message from billi 04-15-2019

See the excerpt below, from the JMP Help select Scripting Index > Objects > search for nonconformance then press the Topic Help button.

Overall Sigma will be larger than Within Sigma, and % out of spec will be larger. If your data is representative of the full population and can be modeled as a normal distribution and your specified control chart subgrouping, then yes 16 out of 1000.

JMP Help:

The Individual Details report for a variable with a normal distribution shows a histogram, process summary details, and capability and **nonconformance** statistics. The histogram shows the distribution of the values, the lower and upper specification limits and the process target (if they are specified), and one or two curves showing the assumed distribution. The histogram in Figure 11.14 shows two normal curves, one based on the overall estimate of standard deviation and the other based on the within-subgroup estimate.

When you fit your process with a normal distribution, the Process Summary includes the Stability Index, which is a measure of stability of the process. The stability index is defined as follows:

(Overall Sigma/Within Sigma)

If Calculate Between-and-Within Capability is specified for a process in the launch window, the stability index for that process is defined as follows:

(Overall Sigma/Between-and-Within Sigma)

A stable process has stability index near one. Higher values indicate less stability.

2 REPLIES 2

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**Note:** You can change the preferences for stability assessment type in File > Preferences > Platforms > Process Capability. This changes the stability assessment type used through the Process Capability platform.

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Created:
Apr 15, 2019 7:01 PM
| Last Modified: Apr 15, 2019 7:02 PM
(4044 views)
| Posted in reply to message from billi 04-15-2019

See the excerpt below, from the JMP Help select Scripting Index > Objects > search for nonconformance then press the Topic Help button.

Overall Sigma will be larger than Within Sigma, and % out of spec will be larger. If your data is representative of the full population and can be modeled as a normal distribution and your specified control chart subgrouping, then yes 16 out of 1000.

JMP Help:

The Individual Details report for a variable with a normal distribution shows a histogram, process summary details, and capability and **nonconformance** statistics. The histogram shows the distribution of the values, the lower and upper specification limits and the process target (if they are specified), and one or two curves showing the assumed distribution. The histogram in Figure 11.14 shows two normal curves, one based on the overall estimate of standard deviation and the other based on the within-subgroup estimate.

When you fit your process with a normal distribution, the Process Summary includes the Stability Index, which is a measure of stability of the process. The stability index is defined as follows:

(Overall Sigma/Within Sigma)

If Calculate Between-and-Within Capability is specified for a process in the launch window, the stability index for that process is defined as follows:

(Overall Sigma/Between-and-Within Sigma)

A stable process has stability index near one. Higher values indicate less stability.

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Re: capability analysis using control chart builder

Thank you gzmorgan0 for the explanation.

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