Posted by Brian on .
A random sample of fortyeight 200 meter swims has a mean of 3:12 minutes and a standard deviation of .09 minute. Construct a 95% confidence interval for the population mean time.
I know u: 3.12, sx: .09, n:48, c:.95
What is the formula I use to find the answer? Can anyone please leave a step by step on how to do it so I can learn and do other problems?

Statistics 
MathGuru,
Formula:
CI95 = mean ± 1.96(sd/√n)
...where ± 1.96 represents the 95% interval using a ztable; sd = standard deviation; n = sample size
Your data:
mean = 3.12
sd = .09
n = 48
Plug the values into the formula and determine the interval.
I hope this will help get you started.