The electrical conductivity &sgr;, thermoelectric powerQ, and Hall coefficientRare examined as a function of the ratio of hole‐to‐electron concentrationsp/nfor a nondegenerate semiconductorat constant temperature. From these relations the fundamental parameters of the material (forbidden band gap, mobilities, and effective masses) can be derived. This approach is particularly applicable to materials whose stoichiometry varies as a function of temperature and vapor pressure of the constituentsP. For any model of this equilibrium decomposition, it is easy to transform the calculations in terms ofp/ninto results as a function ofP. Asp/nincreases, &sgr; passes through a minimum, whileQandRtraverse minimum (negative), zero, and maximum (positive) values. These extrema are of special interest. In the simple case of one kind of imperfection, &sgr;,Q, andRbecome independent ofPin a certain pressure range (i.e., when the intrinsic conditionn=phas been reached). It is then possible to derive the ratio of mobilities &mgr;n/&mgr;pand the ratio of the average effective massesmn*/mp* from &sgr;(P) andQ(P) only. Hence, if &mgr;normn* are known (i.e., from measurements at lower temperatures), one can calculate these parameters for the other charge carrier.