This paper is the result of research carried out by a Working Party set up by the Research Committee of the Institute in conjunction with the Students' Society in June 1967. J. K. Scholey acted as adviser of the Working Party, the members being G. T. Humphrey, F. R. Langham, R. E. Snelson (from February 1968) and J. D. Sparks. F. R. Wales was also a member until his departure to Australia in October 1967. The opinions expressed in this paper are personal to the members of the Working Party.

A great deal of research has been carried out into expected values of qx or into expected number of deaths. Little attention has however been paid to the random variations in mortality rates or to the random variations in the number of deaths. Research in this direction might very well further our knowledge of the mortality process.