concerning morbidity and mortality rates of diseases, Incidence rate = number of new cases in a time period/size of at risk population at midpoint of time period x K. What is an appropriate value for K? Solution Incidence measures the new cases of a disease that develops over a period of time. Hence it is very helpful to estimate and for etiomological purposes. The appropriate value of K is as follows K = 10 ^ n where n = total no . of new cases of a specific disease..