this study, however, the periods of continued observation vary, and from the standpoint of development of a better control program it seems important to study the changes in status of tuberculosis cases currently. In the analysis of such clinical data it is necessary to assemble the observations in a form which takes account of the time during which each case remained under observation. For such accounting some modification of the conventional life table is the most convenient method to use.The procedure followed in calculating the mortality experience will be discussed first. The death rate which it is 'desired to obtain is the rate known in life tables as the " probability of death " (q,x) within a year. dx This is expressed by the ratio qx= -lx where lx is the number present at the beginning of the year and dx is the number of those who died within the year. This statement, however, assumes that all those not known to have died within the year can be known to have survived through the year. In the data available, some of the cases were under observation less than a full year while others moved from the county so that the period of observation terminated within a year after [894]

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