ChiSquared confidence intervals  Confidence Intervals
ChiSquared confidence intervals
Lessons
Notes:
To estimate a population variance a ChiSquared distribution is used,
• ChiSquared: $X^2=\frac{(n1)s^2}{\sigma ^2}$
$n$: sample size
$s$: sample standard deviation
$\sigma$: population standard deviation
$(n1)$: is also called "degrees of freedom"
• ChiSquare table gives critical value area to the right
The Confidence interval for the variance is given by:
• $\frac{(n1)s^2}{X_R^2}$ < $\sigma ^2$ < $\frac{(n1)s^2}{X_L^2}$

1.
Determining Degrees of Freedom
How many degrees of freedom does a sample of size, 
2.
Determining the Critical Value for a ChiSquare Distribution $(X_R^2$ and $X_L^2)$
If a ChiSquared distribution has 8 degrees of freedom find $X_R^2$ and $X_L^2$, with a