# Finding Confidence Intervals for Mean, Variance, and Standard Deviation

• Aug 3rd 2011, 06:53 AM
amathnoob
Finding Confidence Intervals for Mean, Variance, and Standard Deviation
I really need some help with this problem ASAP. Here is the problem word-for-word:
Find the 90% confidence interval for the mean, variance, and standard deviation for the price in dollars of an adult single-day lift ticket. The data represent a selected sample of nationwide ski resorts. Assume the variable is normally distributed.

$59$54 $53$52 $51$39 $49$46 $49$48

• Aug 3rd 2011, 02:40 PM
pickslides
Re: Finding Confidence Intervals for Mean, Variance, and Standard Deviation
Hi there, let's do these one at a time so you fully understand. (Happy)

Your data is normal, but you don't know the population standard deviation

Therefore the confidence interval for the mean is $\displaystyle \bar{x}\pm t_{1-\frac{\alpha}{2}, n-1}\times\frac{s}{\sqrt{n}}$

Where

$n$ is the number of samples

$\bar{x}$ is the sample mean

$s$ is the sample standard deviation

$t$ is the test statistic, and

$\alpha$ is the level of significance

What do you get?