Thursday, March 5, 2009

Hypothesis Testing: The Null and Alternative

What is a hypothesis? Any question that has a cause and effect. Statistics is often used to try answer such questions:

Does IQ relate to school grades?
Does smoking cause cancer?
Do caps protect you from aliens?

All these questions are hypothesis.

To statistically test hypothesis, they must be broken into two parts:
The null hypothesis
The alternative hypothesis

The null hypothesis always asserts the theory is false, while the alternative assumes it is true.

Null: IQ doesn't affect school grades
Alternative: IQ affects school grades

Null: Smoking doesn't cause cancer
Alternative: Smoking causes cancer

Null: Caps do not protect you from aliens
Alternative: Caps protect you from aliens

Null: Not guilty
Alternative: Guilty

Tomorrow we will look at type I and type II errors

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