A group measured the half-life of a radioactive source from 15 independent…
PHYSICS · Multi-part · Fermi University Physics · Scientific Practice & Experimental Methods · Records, communication and the epistemology of evidence · Records, communication and the epistemology of evidence
Measurement and Method, Ch Writing the result, and the integrity of the data behind it
Problem
A group measured the half-life of a radioactive source from 15 independent decay-counting runs on a Geiger counter. They kept only the 10 runs whose count rate best fitted a straight line on a semi-log plot, discarding the other 5 as "wrong", without recording a reason in the notebook and without keeping the raw counts for the discarded runs. Their reported half-life, (58.3±1.1)s at k=2, agrees with a value of 58s for the same source obtained independently by a different method. A classmate says: "The conduct here was fine, because the final answer agrees with the accepted value."
((a)) Say whether this claim is correct, with reason.
((b)) Classify what was done, and state what makes it unacceptable regardless of the agreement.
((c)) State the two additional things that would have had to be true of the record for the exclusion of the 5 runs to be defensible.