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!

Decision:

CorrectType 1 Error

“False Positive”

Type 2 Error

“False Negative”

Null is False

Null is True

Reality:

Correct

Reject Null

Fail to Reject Null

What type of error did the birds make when they listened to Chicken Little?

Decision:

CorrectType 1 Error

“False Positive”

Type 2 Error

“False Negative”

Null is False

Null is True

Reality:

Correct

Reject Null

Fail to Reject Null

What type of error did the birds make when they listened to Chicken Little?

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

Cassandra hypotheses• 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!

Decision:

CorrectType 1 Error

“False Positive”

Type 2 Error

“False Negative”

Null is False

Null is True

Reality:

Correct

Reject Null

Fail to Reject Null

What type of error did the Trojans make when they didn’t listen to Cassandra?

Decision:

CorrectType 1 Error

“False Positive”

Type 2 Error

“False Negative”

Null is False

Null is True

Reality:

Correct

Reject Null

Fail to Reject Null

What type of error did the Trojans make when they didn’t listen to Cassandra?

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

Malthusian Growth Model

Has there been a “Malthusian

catastrophe”?

Ester Boserup• Mid to late 1900s

• “Boserupian Theory”

• Developments or inventions cause jumps in the food supply to match the growing population

Time

Time

Consequences?

Malthusian hypotheses• Null Hypothesis (H0):

Malthus is wrong and catastrophe is not imminent.

• Alternative Hypothesis (Ha):Malthus is correct and

catastrophe IS imminent

Decision:Correct(Malthus is right, and we agreed with him).

Type 1 Error(Malthus is wrong and we agreed with him). Chicken Little

Type 2 Error(Malthus is right and we disagreed with him). Cassandra

Null is False

Null is True

Reality:

Correct(Malthus is wrong and we disagreed with him).

Reject Null

Fail to Reject Null

What would be the consequences of a Type 2 Error?of a Type 1 Error?

Malthus

Decision:Correct(Malthus is right, and we agreed with him).

Type 1 Error(Malthus is wrong and we agreed with him). Chicken Little

Type 2 Error(Malthus is right and we disagreed with him). Cassandra

Null is False

Null is True

Reality:

Correct(Malthus is wrong and we disagreed with him).

Reject Null

Fail to Reject Null

What would be the consequences of a Type 2 Error?of a Type 1 Error?

Malthus

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

Riskiness of Errors• Chicken Little?• Cassandra?• Malthus? (Overpopulation?)

• Climate Change?

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

Decision:

Null is False

Null is True

Reality:

Reject Null

Fail to Reject Null

Climate Scientists are right and we agree with them. Action.

Type 1 Error (Chicken Little)“False Positive”

Consequences?Risky?

Type 2 Error(Cassandra)“False Negative”

Consequences? Risky?

Climate Scientists are wrong and we disagree with them. Inaction.