You Measure the Lifetime of a Random Sample of 25

Multiple Choice

You measure the lifetime of a random sample of 25 rats that are exposed to 10 Sv of radiation (the equivalent of 1000 REM) , for which the LD₁₀₀ is 14 days. The sample mean is x̄= 13.8 days. Suppose that the lifetimes for this level of exposure follow a Normal distribution, with unknown mean μ and standard deviation σ= 0.75 day. A 95% confidence interval for is ______________ the 99% confidence interval for μ.

A) wider than
B) narrower than
C) exactly the same as
D) not significantly different from