Computerized probit analysis for radiation mortality

Abstract

The computerized Statistical Analysis System (SAS) for probit analysis was used in analyzing radiation dose response data. Sixty female and 60 male Sprague‐Dawley rats, aged 80±5 days and weighing 200–250 g each, were randomly assigned to six groups of 10 animals each. Each rat received a single total‐body exposure (rads) of Co gamma radiation of 0, 675, 700, 725, 750, or 775 at a dose rate of 304 rads/min. Mortalities were recorded during a 30‐day interval.

The probit ^LD ₅₀₍₃₀₎ for wale rats was 733 (715–754) rads with a Chi‐square of 5.736 (df =3); values for females were 729 (712–750) rads with a Chi‐square of 3.757 (df = 3). When males and females were combined, the LD,₅₀₍₃₀₎ was 731 (719–744) rads and the Chi‐square was 3.384 (df = 3). The probit analysis indicated that the individual populations of rrale and female rats, as well as their combined population. exhibited no significant deviations from normality. Further, the level of significance revealed that the combined population of male and female rats deviated no more from normality than the individual populations of male and female rats. Slopes and intercepts of males and females were not statistically independent of each other, nor were the combined slope and intercept statistically independent of either of the separate slopes and intercepts.

Key words:

• Probit Analysis
• Radiation Mortality
• Dose‐Response
• Median Lethal Dose

Notes

Present address: Department of Anesthesiology, Stanford University School of Medicine, Stanford, California 94305