Various properties of residual life such as mean, median, percentiles, variance, etc., have been discussed in the literature on reliability and survival analysis. However, a detailed study on the covariance between residual lives in a two component system does not seem to have been undertaken. The present paper discusses various properties of product moments and covariances of residual lives. The
... [Show full abstract] relationships the product moment has with the mean residual life and failure rate are studied and some characterizations are established.