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Determining Sample Size for FDA Verification and Validation Activities

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fda (food and drug administration), ltpd (lot tolerance percent defective), samples and sampling plans, verification (general), validation of machines equipment processes design etc.
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  Post Number #1  
Old 17th September 2009, 10:33 AM
QualityNewbie

 
 
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Please Help! Determining Sample Size for FDA Verification and Validation Activities

Hello,

I'm trying to figure out how to determine sample size for our upcoming V&V activities. Is there a sampling plan that is widely used? I've heard LTPD is common, but was wondering if there were other methods in use.

Thanks in advance for your help!

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  Post Number #2  
Old 17th September 2009, 11:24 AM
Craig H.

 
 
Total Posts: 2,046
Re: Determining Sample Size

Quote:
In Reply to Parent Post by QualityNewbie View Post

Hello,

I'm trying to figure out how to determine sample size for our upcoming V&V activities. Is there a sampling plan that is widely used? I've heard LTPD is common, but was wondering if there were other methods in use.

Thanks in advance for your help!
Could you define what "V&V" is, please?
  Post Number #3  
Old 17th September 2009, 11:34 AM
Qualqueen's Avatar
Qualqueen

 
 
Total Posts: 110
Re: Determining Sample Size

Quote:
In Reply to Parent Post by Craig H. View Post

Could you define what "V&V" is, please?
Verification and Validation activities:

Data verification is conducted to ensure that the data selected is the most appropriate for the application and is properly prepared for the product.

Data validation is conducted to ensure that the data accurately represents how it will be simulated.

I think this is correct

Last edited by Qualqueen; 17th September 2009 at 11:46 AM. Reason: added definitions
Thanks to Qualqueen for your informative Post and/or Attachment!
  Post Number #4  
Old 17th September 2009, 11:51 AM
Ajit Basrur's Avatar
Ajit Basrur

 
 
Total Posts: 6,219
Re: Determining Sample Size

Quote:
In Reply to Parent Post by QualityNewbie View Post

Hello,

I'm trying to figure out how to determine sample size for our upcoming V&V activities. Is there a sampling plan that is widely used? I've heard LTPD is common, but was wondering if there were other methods in use.

Thanks in advance for your help!
Welcome to the Cove

Can you pl give more details on what are you validating ?
  Post Number #5  
Old 17th September 2009, 11:59 AM
Bev D's Avatar
Bev D

 
 
Total Posts: 3,630
Re: Determining Sample Size for FDA Verification and Validation Activities

Verification and validation testing is NOT the same as acceptance sampling (AQL, LTPD, etc.)

I have attached a very brief word doc with sample size formulas that can be used for V&V testing. (It is not all inclusive and does not have the utilization of matched pair testing which can be very powerful for rare events or small differences with reduced sample sizes.


If you post some of your examples we can provide much more specific help on this under discussed topic.
  Post Number #6  
Old 17th September 2009, 03:10 PM
Bev D's Avatar
Bev D

 
 
Total Posts: 3,630
Re: Determining Sample Size for FDA Verification and Validation Activities

OK let's try this again.
Attached Files: 1. Scan for viruses before opening, 2. Please report any 'bad' files by Reporting this post, 3. Use at your Own Risk.
File Type: doc sample size calculations.doc (170.0 KB, 3027 views)
Thank You to Bev D for your informative Post and/or Attachment!
  Post Number #7  
Old 29th September 2009, 05:43 AM
achorste

 
 
Total Posts: 200
Re: Determining Sample Size for FDA Verification and Validation Activities

Thank you very much for helping on this issue Bev.

Maybe I haven't quite got the idea for determining 'delta' - the amount of accuracy that you want - does anyone have a simple worked example they could share? Primarily I'm looking at continuous data.

Many thanks for any help you could give,
  Post Number #8  
Old 29th September 2009, 01:51 PM
Bev D's Avatar
Bev D

 
 
Total Posts: 3,630
Re: Determining Sample Size for FDA Verification and Validation Activities

The "delta" is simply the amount of accuracy you want. You can think of it loosely as the size of a confidence interval. If you are going to compare two things experimentally and you would expect to see non-overlapping confidence intervals if there was a real difference then you can take teh difference between the two as 2Delta...

here is an example of how to use 'delta' in validation. We had a plastic device that had a baseline breakforce average of 19.7 and a standard deviation of 1.81. We wanted to validate two new platic formulations and test their break force to the current process. The specification was 15-25. There was almost no lot to lot variation so we could ignore any lot to lot complications in our sample size determination. We wanted to be able to detect a 1 pound change in force (the spread of the process took almost the entire tolerance range so even a 1 pound change would increase our proportion out of spec.) We selected the standard values for alpha (5%) and beta (10%). We included Beta because we wanted to be sure that we saw a difference as small as 1 pound.
The formula: n = [{(z_a/2 + z_b/2).SD}/Delta]^2 = [{(1.96 + 1.645)1.81}/1]^2 = 43.

We tested three lots; the current plastic and the two new plastics, each test run had n=43. There was no statistically significant difference bewteen the three lots.
Thank You to Bev D for your informative Post and/or Attachment!
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