Posted by April on Thursday, March 26, 2009 at 3:40pm.
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
Formula:
CI90 = mean + or  1.645 (sd/√n)
...where + or  1.645 represents the 90% confidence interval using a ztable, sd = standard deviation, and n = sample size.
Substituting:
CI90 = 38500 + or  1.645 (350/√49)
Finish the calculation.
I hope this will help get you started.