1. Section 2: Estimating with Small Samples
Chapter 8: Estimation
Section 2: Estimating with Small Samples

2. Student’s T Distribution
degrees of freedom df = n – 1
population of x values must be normal or approximately normal
resembles the standard normal curve
total area under curve = 1
centered at 0
symmetric about 0
more spread out than the standard normal curve
as n gets large, df gets large, curve gets closer to the standard normal curve

3. Confidence Interval

4. Example
A company has a new process for manufacturing large artificial sapphires. In a trial run, 12 sapphires are produced. The mean weight for these 12 gems is 6.75 carats, with a standard deviation of 0.33 carat. Find a 95% confidence interval for the population mean.