Scrapie is a degenerative disease of the nervous system. A study of the substance IDX as a treatment for scrapie used as subjects 24 infected hamsters. Twelve, chosen at random, were injected with IDX. The other 12 were untreated. The researchers recorded how long each hamster lived. They reported: Thus, although all infected control hamsters had died by 95 days after infection (mean ± SEM = 89 ± 1.7), IDX-treated hamsters lived up to 120 days (mean ± SEM = 109.2 ± 2.86). Readers are supposed to know that SEM stands for the standard error of the mean. (a) For the group injected with IDX , find: The mean, x¯ = , The standard deviation, s =