Homework Help: Which formula do I use. Megastats Excel Statistics homework problem

1. May 13, 2008

mexicnfmle

1. The problem statement, all variables and given/known data

The Warren County Telephone Company claims in its annual report that “the typical customer spends $60 per month on local and long distance service.” A sample of 12 subscribers revealed the following amounts spent last month.$64 $66$64 $66$59 $62$67 $61$64 $58$54 $66 a. What is the point estimate of the population mean? b. Develop a 90 percent confidence interval for the population mean. c. Is the company’s claim that the “typical customer” spends$60 per month reasonable?

2. Relevant equations

Sample population? 12
Mean=\$63
Confidence Interval 90%

3. The attempt at a solution

I know I can use megastats to solve this problem, I am just drawing a blank on which formula to use. WHen I click on Descriptive statistics, it comes back saying "not enough data selected". I tried Confidence Interval and I tried both:
Sample size-mean
sample size- p

I must be entering something wrong somewhere.
Can someone just tell me which formula to use? I am drawing a blank..

Thanks,
Emily