Abstract: A theory of percent regression analysis is established in this paper.Forecast inter-vals and control regions of population percentiles and percentages can be calculated,and func-tions of the percentiles and percentages may be tested by this theory.Thus reliability and confi-dence level can be considered when test point scattering.A method of combining regression func-tions and sample variances is also presented to make full use of previous data and raise the preci-sion of forecasts and controls.

Key words: regression analysis, reliability analysis, confidence limits