Internal Audit of Internal Calibration Laboratory - Inspection sample size question

[Charles Wathen]

Hi everyone,
I usually post in the ISO17025, but now I have a question on sampling. Here is the deal:

I'm a supervisor of an internal calibration lab. I have 8 technicians that report to me. Part of their evaluations include an internal audit that I perform each month. This audit consists of sampling work performed - calibrations.

During this review of records, I look for several issues:
1. Do they have a training record on file for the calibration being performed
2. Did they follow procedure
3. Any mistakes on the calibration certificate

What I would like to know is how many records should I sample for each tech? The number of calibrations per each tech can vary monthly depending on the area they are calibrating. The average number is between 100-130. I'm currently using a 20% sample, but I feel that is overkill. I also have a couple of techs that don't make mistakes. Should they be included anyway in a sample? I rather concentrate on the ones making the most mistakes.

 

[Tim Folkerts]

Charles,

I have two thoughts along somewhat different tracks.

First, could you remove Issue #1 (concerning training records on file) by improving the process of assigning work to techs? Do you and/or the techs not know what tasks they are currently trained to do? Perhaps posting a simple matrix with tech name and date when retraining in a topic is due would suffice to keep everyone cognizant of what calibrations they are allowed to perform.

Secondly, how you sample depends a lot on what you are trying to accomplish. For example, if you want to look for small shifts in the performance of a specific tech for a specific calibration, then 20 pieces per month per individual is probably not enough! If you want to track general trends with a goal of improving the training for calibrations that cause the most problems, then you could get by with sampling fewer records, and concentraing on those who have made the most mistakes in the past.

Just my $0.02....


Tim F

 

[Hershal]

I believe you may find some value in reducing the volume, at least for the top techs, and when you assess for the average or below average techs, the volume is not the most important thing, what you see and how you can use that to improve your operation is.

Also, the higher the volume, the more time required to do your review. If you are obtaining real value from the reviews for a given tech, OK, but if all the records are great, then you can reduce the volume.

It is not an easy question, but hopefully this will help shed some light on potential solutions.

Hershal