Abstract
In the previous papers, we presented an estimating equation of 28 day strength from the results of earlier test. The equation was derived considering statistical properties of the results of strength test and compliance criteria for the test results. The equation covers the case in which the margin of error is constant for any strength in the correlation between earlier strength and 28 day strength. In this paper, the estimating equation which is applicable to the case in which the ratio of the margin of error to the strength is constant in the correlation between earlier strength and 28 day strength is developped. This equation is derived on the basis that the distance from the regression equation to the estimating equation should be equal to the difference between the standard deviation of the distribution of 28 day strength expected from the distribution of the earlier strength test results and the standard deviation of the distribution of the estimated 28 day strength. Derived equation is as follows; [numerical formula] wher F_<28> : Estimated 28 day strength F_a : Result of earlier test a, b : Coefficients of regression in correlation between earlier strength and 28 day strength k : Coefficient shown in Fig.6 S_r : Standard error coefficient obtained in preparatory experiment on the correlation between earlier strength and 28 day strength
