Environmental tobacco smoke exposure and lung cancer: A systematic review

Figure 3 Forest plots for squamous cell carcinoma and spousal smoking, by region. Estimates of the random-effects RR and its 95%CI are shown separately by region, sorted in increasing order of RR. These are shown numerically, and also graphically on a logarithmic scale. Weights (inverse-variance of log RR) are also shown, expressed as a percentage of the weight for all studies combined. Estimates of RRs, 95%CIs and weights are also shown for each region combined and overall. Studies are identified by the study reference code shown in Table 1, with sex identified by m (male), f (female) or c (sexes combined). In the graphical representation, individual RRs are indicated by a solid square, with the area of the square proportional to the weight RRs shown with a - are calculated using a 0.5 addition to each cell, due to a zero in the 2 x 2 table. RR: Relative risk.