To the extent just described, the p.d.f. of a random variable is not unique. In many problems, however, there will be one version of the p.d.f. that is more natural that any other because for this version the p.d.f. will, wherever possible, be continuous on the real line. For example, the p.d.f. sketched in Fig. 3.4is a continuous function over affecting the probability distribution thatit represents, but these changes would introduce discontinuities into the p.d.f. without introducing any apparent advantages.