1. Differences Between Two Means
Chapter 8
Differences Between Two Means

2. Three Scenarios for Differences Between Means

3. Housing Prices and the Charles River

4. Housing Prices and the Charles River

6. Post Outlier Screen

7. Housing Prices and the Charles River

8. Before
After

9. Normal Distribution
No River
River

10. t-Distribution – Fatter Tails – Smaller Sample Size

11. Null Hypothesis: the mean age of turtles in the Gulf is the same as the mean age of turtles worldwide.
Alternative: Gulf turtles have a different mean age than turtles worldwide.”
Perhaps you’re willing to be wrong 1 time in 20—as statisticians often phrase it, “alpha is .05.”
The mathematics of the t-distribution tells us that 5% of the sample means will be less than or equal to 46.2
The value 46 in this example is called the critical value.
If your sample, the one that you actually take, has a mean of 46 or less, you have decided to conclude that the sample did not come from a distribution that represents the null hypothesis

13. Housing Prices and Charles River

14. Smaller vs. Wider Standard Deviation