Upper and Lower 95% Confidence Interval - The confidence interval is a measure of how certain we can be that the SIR value is true and not just a sampling error. The confidence interval is represented as a range of possible SIR results given the data collected. If the range of numbers includes 1.0, (meaning the number of observed infections and the number of predicted infections was the same), then there are no differences between the reported infections and the national baseline. Any apparent differences in the reported data and the baseline/benchmark may be a result of chance error.