Fig. 3.
Forest plot showing the results of 71 studies estimating prevalence of norovirus asymptomatic infection (τ2 = 0.60, P < 0.01 test for heterogeneity). The figure showed prevalence with 95% confidence intervals in the individual studies based on a random-effects model with studies ordered by prevalence. A line was used to represent the confidence interval of estimate. The prevalence estimated was marked with a solid black square. The size of the square represented the weight that the corresponding study exerted in the meta-analysis. The size of the square and the length of confidence interval corresponded to the size of the study and therefore the precision of the estimate. The pooled prevalence was marked with a filled polygon that had a dotted line from its upper point. Confidence intervals of pooled estimates were displayed as the width of the polygon. N was the number of NoV positive samples, value of 1/2 was added to N for calculation when N was equal to 0.