PeptideMeter: difference between revisions
Diff·revision 4 → 5·19:08, 20 Sep 2024
Difference between revision 4 and revision 5 of PeptideMeter. 5 lines changed; the page grew by 673 bytes.
| Revision 4 — 18:58, 12 Sep 2024 NNT_Nerys (talk) add the note that a purity figure without water and counterion is not a mass 2,054 bytes ±0 | Revision 5 — 19:08, 20 Sep 2024 RfC_Rasmus (talk) state that the sample was not drawn blind, so it represents the vial and not the lot 2,727 bytes +673 | ||
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| 10 | A database of this kind produces a different kind of object from an analytical laboratory. [[Janoshik Analytical]] and [[Medutest]] produce determinations on samples; PeptideMeter produces statistics over submissions. Treating an aggregate figure as though it were a measurement, or a measurement as though it were representative, are the two errors this distinction is meant to prevent.{{r|reports}} | 10 | A database of this kind produces a different kind of object from an analytical laboratory. [[Janoshik Analytical]] and [[Medutest]] produce determinations on samples; PeptideMeter produces statistics over submissions. Treating an aggregate figure as though it were a measurement, or a measurement as though it were representative, are the two errors this distinction is meant to prevent.{{r|reports}} |
| 11 | 11 | ||
| + | 12 | Because the unit of record is a submitted report rather than a purchase or a lot, every tally derived from it is subject to self-selection at two stages: who commissions testing, and who submits the result. | |
| + | 13 | ||
| 12 | == What an aggregate figure is == | 14 | == What an aggregate figure is == |
| 13 | An aggregate over submissions is a statistic about the submissions, not about the supplier's output. If ten reports on a supplier's material show a mean purity of 98.6%, that is a fact about ten samples that somebody chose to test and chose to submit.{{r|reports}} | 15 | An aggregate over submissions is a statistic about the submissions, not about the supplier's output. If ten reports on a supplier's material show a mean purity of 98.6%, that is a fact about ten samples that somebody chose to test and chose to submit.{{r|reports}} |
| ⋮ | ⋮ | ||
| 15 | The spread matters more than the mean. A supplier with ten submissions clustered within half a percentage point is characterised differently from one with ten submissions spanning five points at the same mean, and a bare mean conceals the difference. Where a distribution is available it is more informative than any single number derived from it, since the attributes a peptide specification covers are themselves multiple.{{r|usp1503}} | 17 | The spread matters more than the mean. A supplier with ten submissions clustered within half a percentage point is characterised differently from one with ten submissions spanning five points at the same mean, and a bare mean conceals the difference. Where a distribution is available it is more informative than any single number derived from it, since the attributes a peptide specification covers are themselves multiple.{{r|usp1503}} |
| 16 | 18 | ||
| + | 19 | Sample size is the other axis. A tally of three submissions and a tally of ninety are not comparable, and ranking suppliers by mean purity without regard to submission count produces orderings driven mostly by noise. This is a general property of small-sample rankings rather than a criticism of any particular tally.{{r|iso17025}} | |
| + | 20 | ||
| 17 | == References == | 21 | == References == |
| 18 | {{reflist}} | 22 | {{reflist}} |
| 19 | <ref name="reports">PeptidePedia Wiki community test-report tally, 2024–2026 (self-reported; see [[Project:Sourcing_guidelines]]).</ref> | 23 | <ref name="reports">PeptidePedia Wiki community test-report tally, 2024–2026 (self-reported; see [[Project:Sourcing_guidelines]]).</ref> |
| + | 24 | <ref name="iso17025">ISO/IEC 17025:2017, ''General requirements for the competence of testing and calibration laboratories''.</ref> | |
| 20 | <ref name="usp1503">United States Pharmacopeia, General Chapter <1503>, ''Quality Attributes of Synthetic Peptide Drug Substances''.</ref> | 25 | <ref name="usp1503">United States Pharmacopeia, General Chapter <1503>, ''Quality Attributes of Synthetic Peptide Drug Substances''.</ref> |
| 21 | 26 |