Q 656. An important input while working with control charts is to decide the sample size for monitoring. For e.g. - we could pick a sample of 1 item, 5 items, 20 items etc. How is this sample size decided? What happens if sample size is too low or too high? Note for website visitors - This platform hosts two weekly questions, one on Tuesday and the other on Friday. All previous questions can be found here: https://www.benchmarksixsigma.com/forum/lean-six-sigma-business-excellence-questions/. To participate in the current question, please visit the forum homepage at https://www.benchmarksixsigma.com/forum/. The question will be open until Tuesday or Friday at 5 PM Indian Standard Time, depending on the launch day. Responses will not be visible until they are reviewed, and only non-plagiarised answers with less than 5-10% plagiarism will be approved. If you are unsure about plagiarism, please check your answer using a plagiarism checker tool such as https://smallseotools.com/plagiarism-checker/ before submitting. All correct answers shall be published, and the top-rated answer will be displayed first. The author will receive an honorable mention in our Business Excellence dictionary at https://www.benchmarksixsigma.com/forum/business-excellence-dictionary-glossary/ along with the related term. Some people seem to be using AI platforms to find forum answers. This is a risky approach as AI responses are error prone as our questions are application-oriented (they are never straightforward). Have a look at this funny example - https://www.benchmarksixsigma.com/forum/topic/39458-using-ai-to-respond-to-forum-questions/ We also use an AI content detector at https://crossplag.com/ai-content-detector/. Only answers with less than 15-20% AI-generated content will be approved.

Sample Size in Control Charts: Sample size for control charts is chosen based on factors like process variation, stability, and resource constraints. If the sample size is too low: It may miss important process changes Estimates of process variation may be unreliable If the sample size is too high: It can be costly and time-consuming The chart may overreact to small changes, leading to not meaningful variations Finding the right balance of samples [variable] and range [Time frame] is key for effective monitoring and control. Attaching my practice control chart image, where the sample count [ Week on week Quality Scores ] was enough to determine my process health.

Message added by Mayank Gupta, April 2, 20242 yr

Control Chart is a graphical tool used to determine process performance with time. These were developed by Walter A. Shewhart and hence are also known as Shewhart charts. These charts help determine whether the process is stable or not. If the process is stable, the process will only have inherent variation (Common Cause variation). The region of common cause variation is given by Control limits (Upper and Lower control limits). Any process variation outside these limits is considered as Special Cause Variation.

Sample Size (Subgroup Size) in a control chart is the number of data points collected in a given time period.

An application-oriented question on the topic along with responses can be seen below. The best answer was provided by Sachin Tanwar on 2nd Apr 2024.

Applause for all the respondents - Sachin Tanwar.

Control Charts - Sample Size

Followers

March 29, 20242 yr

Q 656. An important input while working with control charts is to decide the sample size for monitoring. For e.g. - we could pick a sample of 1 item, 5 items, 20 items etc. How is this sample size decided? What happens if sample size is too low or too high?

Note for website visitors -

This platform hosts two weekly questions, one on Tuesday and the other on Friday.
All previous questions can be found here: https://www.benchmarksixsigma.com/forum/lean-six-sigma-business-excellence-questions/.
To participate in the current question, please visit the forum homepage at https://www.benchmarksixsigma.com/forum/.
The question will be open until Tuesday or Friday at 5 PM Indian Standard Time, depending on the launch day.
Responses will not be visible until they are reviewed, and only non-plagiarised answers with less than 5-10% plagiarism will be approved.
If you are unsure about plagiarism, please check your answer using a plagiarism checker tool such as https://smallseotools.com/plagiarism-checker/ before submitting.
All correct answers shall be published, and the top-rated answer will be displayed first. The author will receive an honorable mention in our Business Excellence dictionary at https://www.benchmarksixsigma.com/forum/business-excellence-dictionary-glossary/ along with the related term.
Some people seem to be using AI platforms to find forum answers. This is a risky approach as AI responses are error prone as our questions are application-oriented (they are never straightforward). Have a look at this funny example - https://www.benchmarksixsigma.com/forum/topic/39458-using-ai-to-respond-to-forum-questions/
We also use an AI content detector at https://crossplag.com/ai-content-detector/. Only answers with less than 15-20% AI-generated content will be approved.

Solved by Sachin Tanwar

April 2, 20242 yr

Go to solution

April 2, 20242 yr

Solution

Sample Size in Control Charts:
Sample size for control charts is chosen based on factors like process variation, stability, and resource constraints.

If the sample size is too low:

It may miss important process changes
Estimates of process variation may be unreliable

If the sample size is too high:

It can be costly and time-consuming
The chart may overreact to small changes, leading to not meaningful variations

Finding the right balance of samples [variable] and range [Time frame] is key for effective monitoring and control.

Attaching my practice control chart image, where the sample count [ Week on week Quality Scores ] was enough to determine my process health.