Is this a probability Distribution? If so, find the Mean (mu) and the Standard deviation (a). If this is not a Probability Distribution, let the summation of P(x): (LP(x))= A, then find: A and let that he your missing row, Then find the Usual Values.! Solution The average population during 1994 was (204500 + 215000)/2 = 419500/2 = 209750. Incidence rate refers to the rate of occurrence of new cases of disease in a population over a specified period of time which also means the number of new cases per unit of population. Incidence rate of lyme disease in 1994 = Number of new cases of lyme disease in 1994/ average population during 1994 = 25/ 209750 = 0.011918951 % or, 0.12 % ( on rounding off to 2 decimal places).