Although unavailability and failure frequency are important reliability measures for designing telecommunications networks, having two different reliability measures causes difficulties when their evaluation results contradict each other. To overcome this difficulty, for determining a single reliability measure is proposed. Market share, which is an important management index, was used and the effect of each reliability measure on this index was studied. If we the effect of one of the reliability measures is small enough to be ignored, then the other one is chosen as the single reliability measure. The procedure of the proposed statistical analysis method and test results suggesting that failure frequency is promising as a single reliability measure are discussed.