= Paul Willetts
{disambiguate=analytical chemist}
{c}
<Paul Willetts (analytical chemist)> is an <analytical chemistry> researcher associated with studies of laboratory performance and <analytical sampling>. The recovery-information report lists him at the MAFF Food Science Laboratory in Norwich, establishing the identity independently of unrelated authors with the same name.<Harmonised guidelines for the use of recovery information in analytical measurement by Michael Thompson and others>[Eurachem-hosted text, title page and affiliation 4.]{ref}
With <Michael Thompson>, <Sharron Anderson>, <Paul Brereton> and <Roger Wood (analytical chemist)>, <Paul Willetts (analytical chemist)> studied collaborative sampling of wheat and green coffee from bulk lots. Multiple samplers allowed the study to distinguish variation under different sampling conditions. Between-sampler variation contributed significantly for two wheat analytes; the coffee results showed significant sampling-repeatability variation without a detected significant sampling-reproducibility contribution.<Collaborative trials of the sampling of two foodstuffs, wheat and green coffee by Michael Thompson and others>[Abstract, sampling design and contrasting results.]{ref}
The measurement begins before material reaches the instrument. For an original illustration, two perfectly repeatable preparations might contain $10$ and $14\,\mathrm{mg\,kg^{-1}}$ because the collected portions differ. Repeating each instrument reading a hundred times would not make those portions identical. <Measurement repeatability> within a portion and <measurement reproducibility> across the relevant procedures therefore cannot be inferred from the same replication design.
<Paul Willetts (analytical chemist)> also coauthored the recovery-information guidance. Together these contributions emphasize that <sample matrix>, material selection, preparation loss and stated <measurement uncertainty> belong in the interpretation of an analytical result. They cannot all be assessed by repeatedly reading a single prepared solution.
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