Mean Conf. Int. (t) 01 Post-exposure radiation levels are approximately Normally distributed. The levels (in Sv) of a random sample of three trauma victims who were recently exposed are 5.5, 6.2, and 4.8. A 95% confidence interval for the mean based on these data is O 5.50 ± 1.74 O 5.50 ± 1.42 O 5.50 ± 1.29 O 5.50 ± 1.05