symmetric relative frequency distribution
A distribution is said to be symmetric if the relative frequency (or probability) is the same the same distance either side of its centre, m. Mathematically, the distribution of X-m is then the same as the distribution of m-X.The mean and median of a symmetric distribution are equal.The most important symmetric distribution is the normal distribution, which is unimodal and therefore is symmetric about the mode.athematically, the distribution of X-m is then the same as the distribution of m-X. The mean and median of a symmetric distribution are equal. The most important symmetric distribution is the normal distribution, which is unimodal and therefore is symmetric about the mode.