ABSTRACT
This chapter introduces a concept called a random variable. The mean is a first order statistic since it involves only the first power of the random variable. The probability density function of a random variable contains all of the information about the random variable. A valuable parameter in describing a probability density function is the variability or the dispersion of the function. The variance is a parameter which is related to the variability of the probability density function. In biostatistics, the standard deviation is used more commonly than the variance, and the reader is likely much more at home with the standard deviation than the variance. The variance gives the dispersion of a signal in terms of the square of the deviation. However, it is often desirable to compare the dispersion of a signal with the signal itself. Since the impedance is just a constant, the power is proportional to the square of the amplitude of the signal.
