The expected values and variances for degree-based topological indices in random spiro chains

In this paper, a general method of calculating the expected values and variances for degree-based topological indices in random spiro chains are obtained. Based on the general method, the explicit analytical expressions for the expected values and variances of some important degree-based topological indices in random spiro chains are presented, in which some known results are included. Besides, the expected values and variances for degree-based topological indices in random spiro chains are compared. In the end, the extremal values and the average values for degree-based topological indices of a spiro chain with n hexagons are determined.