Chicken Little hypotheses

3. Chicken Little hypotheses • Null Hypothesis (H0): Chicken Little is wrong and everything is normal. • Alternative Hypothesis (Ha): Chicken Little is correct and the sky is falling!

4. Reality: Null is False Null is True Decision: Type 1 Error “False Positive” What type of error did the birds make when they listened to Chicken Little? Reject Null Correct Type 2 Error “False Negative” Fail to Reject Null Correct

5. Reality: Null is False Null is True Decision: Type 1 Error “False Positive” What type of error did the birds make when they listened to Chicken Little? Reject Null Correct Type 2 Error “False Negative” Fail to Reject Null Correct

6. Cassandra • Granted the power of prophecy by Apollo. • Cursed so that no one would believe her • Prophecy of the Trojan Horse and the Fall of Troy

7. Cassandrahypotheses • Null Hypothesis (H0): Cassandra is wrong and the Trojans are winning the war. • Alternative Hypothesis (Ha): Cassandra is correct and a Greek ambush is imminent!

8. Reality: Null is False Null is True Decision: Type 1 Error “False Positive” What type of error did the Trojans make when they didn’t listen to Cassandra? Reject Null Correct Type 2 Error “False Negative” Fail to Reject Null Correct

9. Reality: Null is False Null is True Decision: Type 1 Error “False Positive” What type of error did the Trojans make when they didn’t listen to Cassandra? Reject Null Correct Type 2 Error “False Negative” Fail to Reject Null Correct

10. Thomas Malthus (~1800) • Economist who studied populations. • Exponential population growth, linear food production (boom and bust) • Positive checks: famine, disease, and war (death) • Preventative checks: Birth control, abortion, and older ages of marriage

11. Malthusian Growth Model

12. Has there been a “Malthusian catastrophe”?

13. Ester Boserup • Mid to late 1900s • “Boserupian Theory” • Developments or inventions cause jumps in the food supply to match the growing population

14. Time

15. Time

16. Consequences?

17. Malthusian hypotheses • Null Hypothesis (H0): Malthus is wrong and catastrophe is not imminent. • Alternative Hypothesis (Ha): Malthus is correct and catastrophe IS imminent

18. Reality: Null is False Null is True Malthus Decision: Type 1 Error (Malthus is wrong and we agreed with him). Chicken Little Correct (Malthus is right, and we agreed with him). Reject Null What would be the consequences of a Type 2 Error? of a Type 1 Error? Correct (Malthus is wrong and we disagreed with him). Type 2 Error (Malthus is right and we disagreed with him). Cassandra Fail to Reject Null

19. Reality: Null is False Null is True Malthus Decision: Type 1 Error (Malthus is wrong and we agreed with him). Chicken Little Correct (Malthus is right, and we agreed with him). Reject Null What would be the consequences of a Type 2 Error? of a Type 1 Error? Correct (Malthus is wrong and we disagreed with him). Type 2 Error (Malthus is right and we disagreed with him). Cassandra Fail to Reject Null

20. Julian Simon • Economist • Consequences of Type 1 error: slowing of economic growth • Human ingenuity the scarcest resource • Growth and development are the answer to our problems

21. Riskiness of Errors • Chicken Little? • Cassandra? • Malthus? (Overpopulation?) • Climate Change?

22. Climate hypotheses • Null Hypothesis (H0): Climate Scientists are wrong and catastrophe is not imminent. • Alternative Hypothesis (Ha): Climate Scientists are correct and catastrophe IS imminent

23. Reality: Null is False Null is True Decision: Type 1 Error (Chicken Little) “False Positive” Consequences? Risky? Climate Scientists are right and we agree with them. Action. Reject Null Type 2 Error (Cassandra) “False Negative” Consequences? Risky? Climate Scientists are wrong and we disagree with them. Inaction. Fail to Reject Null