IOSH forums home
»
Our public forums
»
OSH discussion forum
»
Double-gloving conundrum - one for the mathematicians
Rank: Guest 
|
Posted By srd
If a batch of 100 disposable gloves were tested and found to have a 2% failure rate, what would the failure rate then be if double-gloving were used (the practice of wearing one glove over the top of the other)?
It would obviously depend on the likelihood that 2 of the faulty gloves were selected at the same time, but being mathematically challenged I can't work it out.
Any offers please?
Stephen.
|
|
|
|
|
|
Rank: Guest
|
Posted By Paul Leadbetter
Isn't it 2% of 2% - 4 in 10,000?
Paul
|
|
|
|
|
|
Rank: Guest
|
Posted By Kate Graham
Assuming that the faulty gloves occur at random within the batch, then you multiply the chance that the first one is faulty (2 in 100) by the chance that the second one is faulty (2 in 100) giving (as above) 4 in 10,000 or 0.04%.
But in practice, whatever it is that causes the gloves to be faulty is quite likely to mean that a glove next to a faulty glove is also going to be faulty. For example if a parameter in the manufacturing or packing process drifts from its ideal value and then is corrected, there may be a run of faulty gloves. In that case the chance of two gloves pulled one after another out of the box both being faulty will be higher than 0.04%. But it's not possible to calculate what it will be without knowing the pattern in the faults.
Kate
|
|
|
|
|
|
Rank: Guest
|
Posted By robert prince-wright
it depends a little on the semantics. When they say 2% of the gloves were defective do they mean pairs of gloves or individual gloves?
|
|
|
|
|
|
Rank: Guest
|
Posted By Peter Leese
Are you sure you don't mean pedantics?
|
|
|
|
|
|
Rank: Guest
|
Posted By Chris Packham
If the purpose of this question is to help assess the significance of any pucture in terms of risk to the wearer, one fact that will be important is the nature of any exposure.
I have pictures from a study by NIOSH (I believe as yet unpublished) that were kindly provided for me to use when training on glove usage. These show clearly the difference in spread of contamination on the hands depending upon the nature of the exposure. Comparisons were made between wiping with a moistened towel and immersion. The difference in skin exposure is substantial.
Chris
|
|
|
|
|
|
Rank: Guest
|
Posted By Tabs
As the coarsest measure, I agree with the 20% of 20%. But that is for the whole population of gloves - but as already pointed out, you could have a month of bad production in 5 months of good production.
So before you can calculate the likelihood of two punctured gloves meeting on a single hand, you need to know the distibution. So you need to know what the manufacturer bases 20% on.
|
|
|
|
|
|
Rank: Guest
|
Posted By Peter Leese
You've lost me, where did the 20% figure come from?
|
|
|
|
|
|
Rank: Guest
|
Posted By Tabs
Ooops! sorry, still dreaming about finishing the Easter Chocs, please read as 2% of 2%
Just going to start a hundred lines "I must pay attention whilst doing things"
|
|
|
|
|
|
Rank: Guest
|
Posted By srd
In answer to Robert Prince-Wright, the 2% failure was for single gloves and not pairs, ie on testing 100 single gloves, 2 failed.
Thanks for all of your replies. Just to make it clear, the 2% failure rate was based on my own testing of 100 single disposable nitrile gloves.
I appreciate that I am talking about a very, very small sample which may not be representative of a much larger sample.
I was trying to calculate the % difference between the likelihood of a single glove failing compared to both gloves if used in double-gloving.
Stephen.
|
|
|
|
|
|
Rank: Guest
|
Posted By Robert K Lewis
SRD
On the basis of your information the figures you have discovered are, as you realise, post manufacturers own quality control. I think that the failure rate you have found is high enough to open discussions with the manufacturer in order to understand in detail the failure causes. You may find that they do not intend these to be used in safety critical areas and thus accept the higher failure figure.
Your work highlights the fact that we all need to very aware of such things when gloves are selected for a particular task. Price is aften the best guide to potential failure rates, buit then if it is not critical then failures can be acceptable.
Bob
|
|
|
|
|
|
Rank: Guest
|
Posted By Chris Packham
I assume that we are dealing here with the thin, single-use nitrile gloves.
There is an "official" method of describing the number of pinholes in gloves, the AQL, or "Acceptable Quality Level". This defines the number of pinholes that are permitted per 100 units.
Level 1 gives an AQL of 4.0 equivalent to less than 4 faults per 100
Level 2 gives an AQL of 1.5 equivalent to less than 1.5 faults per 100
Level 3 gives an AQL of 0.65 equivalent to less than 0.65 faults per unit.
I know of one manufacturer who pressure tests all his single-use nitrile gloves and rejects any with holes. His AQL is therefore 0 - although such a rating does not officially exist.
So when purchasing this type of glove it is worth ensuring that the gloves you are buying are of the appropriate AQL.
If you need to know more on this, contact me direct.
Chris
|
|
|
|
|
|
Rank: Guest
|
Posted By srd
Thanks all.
Stephen.
|
|
|
|
|
|
IOSH forums home
»
Our public forums
»
OSH discussion forum
»
Double-gloving conundrum - one for the mathematicians
You cannot post new topics in this forum.
You cannot reply to topics in this forum.
You cannot delete your posts in this forum.
You cannot edit your posts in this forum.
You cannot create polls in this forum.
You cannot vote in polls in this forum.