#test-results 2024-12-01

does a bad result on one lot condemn the whole supplier

Reminder set. I will post here in 3 days.

a point or two between the certificate and an independent result is inside what two labs disagree by, take that with a pinch of salt

certificate said 97.4 and the independent came back 98.1, is that a problem

i had a result i am fairly sure was a handling error on my side and i logged it as such
update from 22 months ago: retested the same supplier, result came back better, logged both

a supplier disputing a result is rare here and it has never gone well for the supplier

coming back to this what interests me is when the gap goes the same direction every time. once is noise, three times is a pattern

do the results in this channel skew because people test when suspicious

nice result

Verification log updated: GGPeps — evidence added, status unchanged.

the honest limits: hobby chain of custody is weak and any result here should be read with that in mind

which lab

the widest spread in my data is about 2.6 percentage points across five lots from one supplier

my read after three years of this: purity is mostly fine across the market and fill consistency is where suppliers differ

sample handling on your end absolutely affects it. draw cleanly, ship fast, do not let it sit warm

test it again

whats the lot

thats a fill problem

post the lot, the purchase month, the lab, the number, and what you were expecting. that makes it useful later

a result without a lot number and a purchase date is an anecdote with a pdf attached, your mileage will differ

thats within range

log the lot number

if the vial has been through a bad transit you are testing the transit as much as the supplier

the results in this channel skew because people test when they are suspicious. that is selection bias and it is real
one bad test does not condemn a supplier. one good test does not clear one. both halves get ignored equally

how do you separate batch variance from supplier variance