2. A certain drug causes kidney damage in 4% of patients. If 500 patients are administered the drug, approximate the probability that at least 25 will have kidney damage. Use the continuity correction factor. Solution Prob for causing damage to kidney = 4% =0.04 No of patients that were administered the drug = 500 As no of patients increase this binomial approximates to Poisson with continuity factor np = lemda i.e. mu = 500(0.04) = 20 P(X>=25) =0.1568.