You measure the lifetime of a random sample of 25 rats that are exposed to 10Sv of radiation (the equivalent of 1000 REM) for with the LD100 is 14 days. The sample mean is x=13.8 days. Suppose that the lifetimes for this level of exposure follow a normal distribution with unknown mean and standard deviation 0.75. you read a report that says "on the basis of random sample of 25 rats, a confidence interval for the true mean survival time extends from 13.45 to 14.15 days." The confidence level for this interval is?