selection bias
#test-results 2026-06-29
Monday46 messages9 participantstimes are UTC
Highlights from this day
- VialBot — Verification log updated: WXT — evidence added, status unchanged. 16:45
- ms_ms_mira — my result contradicts the supplier certificate, do i tell them 16:46
- deamidation — post the lot, the purchase month, the lab, the number, and what you were expecting. that makes it useful later 17:28
- deamidation — my sheet has 3 lots from JEEP with a spread under a point, which is tight 18:52
a supplier disputing a result is rare here and it has never gone well for the supplier
log the boring results too. a channel that only records failures produces a false picture, ymmv
when did you buy it
whats the underfill rate people are actually seeing
coming back after 11 months with a follow up result, where do i put it
weigh the vial before you reconstitute. it costs nothing and catches the common failure
do you test every order or sample it
[edited]log the boring ones
assay under label with good purity means you got less of the right thing. that is a fill problem, not a synthesis problem
Verification log updated: WXT — evidence added, status unchanged.
my result contradicts the supplier certificate, do i tell them
the honest limits: hobby chain of custody is weak and any result here should be read with that in mind
unrelated but how much does sample handling on my end affect the number
📉5
has a supplier ever disputed a result posted here
i have never regretted spending the money on a test. i have regretted not testing twice
🤝5
do the results in this channel skew because people test when suspicious
which lab
post the lot, the purchase month, the lab, the number, and what you were expecting. that makes it useful later
💀4🎉5🧊3
one bad test does not condemn a supplier. one good test does not clear one. both halves get ignored equally
whats the lot
*Medutest not the other one
a point or two between the certificate and an independent result is inside what two labs disagree by
right so if the vial has been through a bad transit you are testing the transit as much as the supplier
slightly off topic but 99.2 against a certificate of 99 is fine. the same supplier landing low four times in a row is a question, happy to be corrected
underfill is more common than impurity. if you only test purity you are testing the less likely failure
thats a fill problem
| Evidence | Counts? |
|---|---|
| Independent report, lot you bought, lot number legible | yes |
| Independent report, no lot number | no |
| Supplier certificate only | no |
| Screenshot of a report | no |
| Blinded pooled submission | yes, for the pool |
| A friend who said it was fine | no |
thats within range
the results in this channel skew because people test when they are suspicious. that is selection bias and it is real, for what its worth
🎉2📈4
the widest spread in my data is about 2.6 percentage points across five lots from one supplier
for the archive my vial assayed under label but the purity was fine, which matters more
one data point
thats not great
sample handling on your end absolutely affects it. draw cleanly, ship fast, do not let it sit warm
Channel stats, last 30 days: 41 messages from 48 members.
my sheet has 3 lots from JEEP with a spread under a point, which is tight
🧊1💀2🤝1
how many lots do you need before you can say anything about a supplier
follow up i had a result i am fairly sure was a handling error on my side and i logged it as such
quantity testing is usually a separate line item and it is the one worth paying for
log the lot number
😂8
attach the pdf
⚠️2🧪1
unrelated but i test roughly every tenth vial. it is a sampling strategy, not paranoia
i told KP about a result they would not have liked and they did not argue. credit where it is due
a single sample tells you about a single vial. that is genuinely all it tells you
anyone tested the same lot twice at different labs