1. 6.2 Confidence Intervals for the Mean ( unknown)
Key Concepts:
Properties of the t-distribution
Finding Areas Below a t-curve
Building and Interpreting Confidence Intervals for the Mean

2. 6.2 Confidence Intervals for the Mean ( unknown)
What is the t-distribution?
William S. Gosset
“Studentized” version of the sample mean
If X is normally (or approximately) normally distributed, then the studentized version of the sample mean
follows a t-distribution with n-1 degrees of freedom

3. 6.2 Confidence Intervals for the Mean ( unknown)
Properties of the t-distribution
Bell-shaped and symmetric
Shape of the t-curve is determined by the number of degrees of freedom
Total area below every t-curve is 1
Mean, Median, and Mode are all zero
As the number of degrees of freedom increases, the t-distribution approaches the standard normal distribution

4. 6.2 Confidence Intervals for the Mean ( unknown)
Practice working with t-curves
#2, 4 p. 315
How do we build these confidence intervals?
Note: When we construct “t-intervals”, we use the t-curve with
n – 1 degrees of freedom.

5. 6.2 Confidence Intervals for the Mean ( unknown)
Practice:
#18 p (Driving Distance to Work)
#28 p (Homework)
How do we know whether a z-interval or a t-interval is more appropriate?
Flowchart on p. 314 will help
More practice:
#34 p (Yards Per Carry)
#31 p (Body Mass Index))