=+67. A study was carried out to investigate the relationship between brightness of finished paper (y) and the variables percentage of H2O2 by weight, percentage of NaOH by weight, percentage of silicate by weight, and process temperature (“Advantages of CEHDP Bleaching for High Brightness Kraft Pulp Production,” TAPPI, 1964: 170A–173A). Each independent variable was allowed to assume five different values, and these values were coded for regression