1. Ungerleider, H. E., and E. V. Higgins: Prognosis of cardiovascular disease: An insurance appraisal. Amer. J. Cardiol. 13, 576 (1964).
2. The statement that the mortality is 150 percent is an oversimplification. The mortality-ratio depends not only on the numbers of deaths, but also on their distribution over the period of observation. In the present example where no information is supplied about the incidence of mortality it seems reasonable to assume that the force of mortality of the impaired group bears a constant ratio to the force of mortality of the standard group. In that case the constant ratio is the mortality ratio MR and this may be computed, on the lines set out in this paper, as follows: It will be noted that there is no material difference between and Such differences do, however, arise when lower survival rates are in-volved.
3. This means and is equivalent to the more general formula In either case the limit is.
4. l
55½. and l
55¼ computed by interpolation from l
54, l
55, l
56, l
57.
5. Proof: consequently qx≈ μx+ ½ + terms involving higher powers of μ. The error involved in writing q
x = μx + ½ is of the order ½ (μx + ½)2. Values of q
x or μx should not exceed 0.20 if errors exceeding 10 percent of q
x or μx are to be avoided.