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UPSC Combined Geo-Scientist

Chemist

  • 3 descriptive papers
  • 200 marks each
  • 3 h per paper

Mains Paper III covers analytical and organic chemistry.

UPSC Combined Geo-Scientist, Mains · 2021 · Mains Paper III

Q5(a). Accuracy and precision of two analysts; types of error

Question

A substance was known to contain 49.10 ± 0.02% of a constituent ‘A’. Two analysts attempted to determine ‘A’ using the same substance and the same analytical method. The results obtained by them were as follows: First Analyst: % A 49.01, 49.25, 49.08 and 49.14; Second Analyst: % A 49.40, 49.44, 49.42 and 49.42. Compare their accuracies and precisions. Identify the types of errors associated with their analyses.

Answer in brief

First analyst: mean 49.12 %, accurate but not precise (random errors). Second analyst: mean 49.42 %, precise but not accurate (systematic error of +0.32 %).

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Topic notes: errors in chemical analysis, standard deviation, confidence limits and the Q-, t- and F-tests, with every Civil Services, IFoS and Geo-Scientist PYQ →

Coversaccuracy and precisionsystematic errorrandom errorstandard deviationt-test

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