This in-depth presentation of current analytical methods for optimal design, selection, and evaluation of instrumentation for process plants is clear, concise, and systematic-providing a valuable tool for improving quality, costs, safety, loss prevention, and production accounting. The author concentrates on determining the optimal set of measured variables and selecting the accuracy and reliability of the corresponding instruments. The goal is to observe and diagnose single and multiple process faults and to obtain sufficiently accurate and reliable estimates of variables of interest while filtering bad data caused by possible instrument malfunction.