The average price for new mobile homes is known to be distributed with a standard deviation of 350. if a random sample of 49 homes resulted in a sample mean of 38500, obtain a 90% confidence interval on the population mean.
statistics - MathGuru, Friday, March 27, 2009 at 9:19am
CI90 = mean + or - 1.645 (sd/√n)
...where + or - 1.645 represents the 90% confidence interval using a z-table, sd = standard deviation, and n = sample size.
CI90 = 38500 + or - 1.645 (350/√49)
Finish the calculation.
I hope this will help get you started.