A measured value has little or no true meaning and thus, it is useless, unless the figures (digits) in that value were deemed to be significant and the significant figures were properly determined and reported. Deciding the appropriate number of significant figures for the reporting of numerical data is not an obvious or easy task.
Poisons are among the favorite weapons of mystery writers, if not murderers. Guns may be quicker, but poisons have a cachet that you really can't beat. On the other hand, murder by poison has become increasingly dangerous - to the perpetrator!