Method and apparatus for calculating confidence intervals

This invention relates to prediction interval calculators and, more particularly, to a prediction interval calculator that performs a complete statistical analysis of the output of an atomic absorption instrument in accordance with Six Sigma. An exemplary embodiment of the present invention is a method for calculating at least one confidence interval. The method comprises a set of instructions that activate a calculator. The user selects input data, which the calculator reformats to generate output data. The calculator then generates both a calibration summary and specific calibration summary containing calibration standard measurements from the output data. A linear calibration curve and residual calibration value plot are derived from these calibration standard measurements. The calculator calculates a back-calculated unknown sample value using the information gathered from the linear calibration curve and residual calibration value plot. The calculator can then calculate the confidence interval for the back-calculated unknown sample value.