The pertinent results of a step-wise multiple regression analysis using equation [6] and the data of Fig. 1 through 4 are shown in Table 7 with the model variables listed in the order of their relative contributions. It was found that all of the model variables of equation [6] sufficiently improved the model to warrant inclusion in the model at a level of significance of 5%. The regression coefficients and standard error of estimates for the model variables were: