A power-law path-loss model for indoor communications at 1.8 GHz is examined. In it, the exponent of the distance is treated as a random variable and its behaviour studied through experiments conducted under various propagation conditions in different buildings. The effects of random human traffic in the propagation channel, as well as those of antenna polarization are also experimentally studied. The statistical behaviour of the exponent and its fitting to several distribution functions, in particular Weibull, Nakagami and gamma ones, are also reported. By using the proposed model, new, simple and efficient instruments can be developed as an aid for the estimation of the power budget of indoor wireless communication systems.