Following the approach of the Section 812 Prospective Report , we estimated the percentage change in the prevalence rate for chronic bronchitis using the estimated coefficient from Schwartz 's study in a C-R function , and then applied this percentage change to a baseline incidence rate obtained from another source .
Following the approach of the report , we guessed that the percentage change in the prevalence rate for chronic bronchitis using the coefficient from the study , but found that the result was about 40 % too low .