Confidence level and confidence intervals
We apply the 95 percent confidence level as the generally accepted level of certainty used in statistical tests. Any sample may produce estimates that differ from the figures that would have been obtained if the whole population had been examined. At the 95 percent confidence level, with many repeats of an audit under the same conditions, we expect the confidence interval would contain the true population value 95 times out of 100.
The confidence interval provides an estimated range of values that the given population being examined is likely to fall within. For example, if an audit found that 85 percent of crimes were correctly recorded with a confidence interval of +/–3 percent, then we could be confident that between 82 percent and 88 percent of crimes were correctly recorded of the population for the period being examined.« Back to Definitions and Interpretations