# Determining Sample Size and Frequency for Features on Control Plans

G

#### George Trybulski

When developing control plans, is there a "standard" way to come up with a sample size for a peticular feature. I don't agree to base it on quantity of the order but should it be on the critical nature of the dimension ?

#### Marc

##### Hunkered Down for the Duration
Staff member
I don't know of a 'standard'. It depends upon the type of process, how critical the dimension is, how stable the process is and what you are trying to do in general.

Are you thinking SPC here?

B

#### BILLYLEU

Originally posted by chen:
don't forget to consider the output RPN of FMEA.
I am a rookie in the the field of quality control field. Could somebody help to the defination of DOE ,QFD , RPN ,ASO and AIAG?

#### Marc

##### Hunkered Down for the Duration
Staff member
DOE = Design of Experiments

QFD = Quality Function Deployment

RPN = The number obtained in an FMEA when you multiply the 3 factors of that FMEA type. I think the acyronym is something like Resultant Priority Number

ASO = I have no idea

AIAG = Auto Industry Action Group

S

#### SAMOON

Re: Determining Sample Size and Frequency for the Control Plan

RPN= Risk Priority Number

#### Marc

##### Hunkered Down for the Duration
Staff member
When developing control plans, is there a "standard" way to come up with a sample size for a particular feature. I don't agree to base it on quantity of the order but should it be on the critical nature of the dimension ?
This is an old thread which "bubbled up". Would anyone care to comment on the starting post since it was never adequately answered?

S

#### ssz102

according with my experience, the size of sampling depends the type of product your production or how does the product are manufacturing?
generally speaking, sampling 3---5pcs for cosmetic, and approximate 5pcs for measurement studies, and about 1--2pcs as function or performance analysis

#### ranvir.jaryal

##### Registered Visitor
1. Based on the criticality of a particular dimension, there will be an AQL (Normally customer driven).
2. Then taking into consideration, your process capability, appropriate sampling plan should be reviewed and implemented.
3. During initial stages of new product, sampling should be done tightly.
4. Thereafter at regular intervals, based on the data available, sampling frequency should be reviewed and updated.
5. DO not forget to update frequency in Control Plan also.

This approach will also help keeping Control Plan a live document.

For sampling plan please refer to MIL-STD 105E

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