Question

An article in Cancer Research "Analyses of littermatched time-to-response data, with modifications for recovery of interlitter information," (1977, Vol. 37, pp. 3863-3868) tested the tumorigenesis of a drug. A total of 41 rats were randomly selected from litters and given the drug. The times of tumor appearance were recorded as follows: 101, 104, 104, 77, 89, 88, 104, 96, 82, 70, 89, 91, 39, 103, 93, 85, 104, 104, 81, 67, 104, 104, 104, 87, 104, 89, 78, 104, 86, 76, 103, 102, 80, 45, 94, 104, 104, 76, 80, 72, 73 Calculate a 99% confidence interval on the standard deviation of time until a tumor appearance. Assume population is approximately normally distributed. Round your answers to 2 decimal places. 153.23 494.01 о

Answer 1

here n = s? 255.7756 Critical value for 40 degree of freedom and 99 % CI are as follows XEE X 0.005 X 0.995 x?u= Variance Ci= 20.707 66.766 (n-1)s/X1 (n-1)/xu Variance CI 153.2370 <o<= 494.0853 Std deviation CI 12.3789 <=O<= 22.2280

from above 99% confidence interval =12.38 < $\sigma$ <22.23