Fitting a Concentration-Response Curve
The midpoint is only as good as the plateaus. What the four-parameter model assumes, which fitting decisions move the answer, and how to read a reported value.
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How research peptide identity and purity are verified, and how to read the supporting analytical documentation.
The midpoint is only as good as the plateaus. What the four-parameter model assumes, which fitting decisions move the answer, and how to read a reported value.
An assignable cause independent of the value is the only defensible basis. Why statistical tests do not settle it, and why deciding in advance is the whole discipline.
Three wells from one dilution are three measurements of one thing. Why counting them as the sample size inflates confidence, and what actually counts as independent.
Three different quantities, routinely unlabelled and differing by a factor of two or more. What each describes, why overlap does not mean what it looks like, and what n refers to.
A p-value is a statement about data given a hypothesis, not the reverse. The four misreadings, why effect size is the number that matters, and the multiplicity problem.
An unexpected peak is sometimes a different peptide introduced during preparation. The routes that account for most of it, how to tell it apart, and what removes it.
Peptides bind to glass, plastic, tips and filters. Why the proportion lost depends on concentration, why selective loss changes a measured purity, and what reduces it.
A certificate describes one lot. Why consistency across lots is the question it cannot answer, what trending shows, and the partial version a buyer can assemble.
Why 98.7% and 98.70% are different claims, where rounding belongs in a calculation, and how a rounding convention decides whether a borderline lot passes.
Why a failing result cannot be replaced by a passing one, what an out-of-specification investigation is for, and the three things a retest is not.
A specification is an attribute, a method and an acceptance criterion. Where the criterion comes from, why the method must be capable of it, and what it leaves unconstrained.
Why two tests only count as two when they could have disagreed for independent reasons, which pairings are genuinely orthogonal, and where independence fails quietly.
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