A Study Is Going to Be Conducted in Which the Mean

Multiple Choice

A study is going to be conducted in which the mean of a lifetime of batteries produced by a certain method will be estimated using a 90% confidence interval.The estimate needs to be within +/- 2 hours of the actual population mean.The population standard deviation σ is estimated to be around 25.The necessary sample size should be at least _______.

A) 100
B) 21
C) 923
D) 35
E) 423