 Lloyd A. Currie

Lloyd A. Currie prepared the 1995 IUPAC recommendations on evaluating analytical methods, including detection and quantification capabilities. A central contribution was to separate an observed-result decision from the capability of a measurement process. A detection decision threshold controls the chance of a false positive, while a limit of detection also depends on the chance of missing a real signal.^[ref]

An original idealized example makes the distinction visible. Suppose the blank-corrected measurement has a normal distribution with standard deviation one. A threshold near $1.645$ gives a 5% type I error under a zero-mean blank model. A true mean near $3.29$ places that same threshold about $1.645$ standard deviations below the mean, giving about 95% detection probability, or 5% type II error.

The two signal levels answer different questions: whether one observed result crosses a decision boundary, and how strong a true signal must be for reliable detection under the assumed process. These numbers belong to the stated model; they are not universal detection limits for instruments.