AbstractCorrelated neutron fluctuation experiments have been performed on a poorly coupled, multiple seed-blanket reactor and on a better coupled cylindrical lattice reactor. The fluctuating numbers of counts recorded in various gate times by separated detectors are analyzed in terms of a proposed measure of reactor coupling, the modified coefficient of correlation,MCC, as well as in terms of the conventional dispersion parameterY. Effects of count losses, statistical bias, and statistical error are examined. Calculations ofMCCandYare carried out in theα-mode form of the product density formalism for a number of detailed reactor models, including several four-energy-group diffusion theory andP-3 transport models for reactor design. Two of these detailed models, incorporating reduced fast-neutron transport and removal cross sections, are in agreement withMCCmeasurements, while one design model is not.