Precision estimation and sample size planning to test influenza A H1N1 positive rate

Using the data in the influenza A H1N1 positive rate of sampling from August 3,2009 to November 14,Beijing,we estimated the precision of absolute error and relative error.During the epidemic,absolute error of the H1N1 positive rate was less than 0.1 under the confidence level of 1-α = 0.95,this error was at a controllable level.The relative error of the H1N1 positive rate was large at the early phase of influenza A H1N1 transmission, 0.5 before 37 weeks.With the development of the epidemic,the relative error decreased gradually,which means that the result tends to be a reliable estimate.The relative error was less than 0.2 after 42 weeks.Finally,this paper provided a sample size planning based on precision control for sampling test of positive cases.We argued the marginal changes in sample size with a series of conditions.Optimal sample sizes were estimated under different combinations of positive rate and absolute error.