Scrapie treatment, delay of symptoms. Scrapie is a prion disease similar in pathology to bovine spongiform encephalopathy (mad cow disease) and new variant Creutzfeldt-Jakob disease. In a study of 20 scrapie-infected hamsters, 10 were treated with a substance known as IDX and 10 were left untreated. The mean time before appearance of symptoms in the control group was 81.9 days (SE1 = 2.2 days). The mean time to symptoms in the treated group was 102.8 days (SE2 = 3.8 days).j Test this difference for significance. Note that group standard errors (not standard deviations) are given in this problem.

To calculate the standard error of the mean difference, apply this formula: