Standardized Mortality Ratios (SMRs) and their 95% approximate confidence intervals (lung cancer mortality in the province of Lecce, 1992–2001). All areas have been ordered in a descending order based on the SMR value, and of these only the first 30 were considered for the graphic representation. Statistical significance refers to the null hypothesis of no increased risk H0 : θ
= 1, where the alternative hypothesis is Ho: θ
> 1. The horizontal dashed line indicates the no increased risk line: it is worth noting that due to the approximation used for the construction of confidence intervals, the lower end may fall below that line (although a few decimal places only) even when significance is reached.