1. The Language of Statistical Decision Making
Lecture 1
Section 1.3
Fri, Sep 1, 2006

2. I Don’t Feel Your Pain!
Study: Men Enjoy Watching Bad Guys Suffer

3. Man or Woman?
Suppose we are not told a subject’s sex, but we are told that the subject felt empathy for the cheater.
Would we guess that the subject is a man or a woman?
Why?
Would we necessarily be correct?

4. Populations and Samples
Statistical inference

5. Samples and Inferences
Population

6. Samples and Inferences
Population
Take
Sample
Sample

7. Samples and Inferences
Population
Take
Sample
Make Observations
Sample
Data

8. Samples and Inferences
Population
Inference
Draw an
Inference
Take
Sample
Make Observations
Sample
Data

9. Samples and Inferences
Population
Inference
Draw an
Inference
Take
Sample
Make Observations
Sample
Data

10. Hypotheses Hypothesis
A hypothesis is often a statement that is proposed to explain something that is known to be true.

11. Hypotheses
The Null Hypothesis – The conventional belief about the population, or the status quo, or the neutral position.
It receives the benefit of the doubt.
The Alternative (Research) Hypothesis – An alternative to the null hypothesis.
It bears the burden of proof.
Typically, the researchers are trying to prove the alternative hypothesis.

12. Hypothesis Testing
Population

13. Hypothesis Testing
Null
Hypothesis
Population

14. Hypothesis Testing
Null
Hypothesis
Population
Alternative
Hypothesis

15. Hypothesis Testing Null Hypothesis Population Alternative Hypothesis
Sample

16. Hypothesis Testing Null Hypothesis Population Alternative Hypothesis
Sample
Evidence

17. Hypothesis Testing Null Hypothesis Population Alternative Hypothesis
Which
Hypothesis Is
Supported?
Sample
Evidence

18. Hypothesis Testing Null Hypothesis Population The evidence may support
the Null
Hypothesis…
Sample
Evidence

19. Hypothesis Testing Null Hypothesis Population …if any discrepancy
can be
attributed
to chance
Sample
Evidence

20. Hypothesis Testing Population Alternative Hypothesis The evidence will
support the
Alternative
Hypothesis…
Sample
Evidence

21. Hypothesis Testing Population Alternative Hypothesis …if the
discrepancy
cannot be
attributed
to chance
Sample
Evidence

22. Statistical Significance
The data are called statistically significant if their deviation from what would be expected under the null hypothesis is too great to be attributed to chance.
Example: The incidence of cancer in one community is 8% and in another community it is 10%. Can the difference be attributed to chance?