Lehto and Carpenter performed a set of experiments concerning the temperature and the gamma-ray fluctuations in a relatively low power reactor with high fission product inventories. The results are uniformly and quantitatively analyzed by applying the theoretical approach previously developed by the present author. The new features of the present consideration are the following two points: (a) incorporation of the external noise source in the previous theory which includes only the inherent noise source theoretically determined with the use of the first-order linearized Markoffian model of the reactor noise phenomenon; (b) analysis of the cross power spectral density (CPSD) between the two state quantities characterizing the core performances. The first point gives a successful interpretation of most of the experimental results in spite of adopting a simple analytical model. The newly extended framework of the theory can include also a reactivity transfer-function analysis with the use of a proper driving function. The phase of the CPSD between the power and the temperature is calculated on a one-space-point, a one-delayed-group, and a one- or two-feedback-loop reactor model. The results suggest that the experimental determination of the phase will provide both a check point for the theoretical model of the dynamical behaviors of at-power reactors and some bits of information on the feedback parameters.