- The
*null hypothesis*. This is the hypothesis under which we will evaluate the data. is a statement about the distribution underlying the data. - The
*alternative hypothesis*. This is an alternative statement about the data distribution. The goal of a hypothesis test is to choose between and . - The
*test statistic*. This is a function of the data (a random variable) with the following two properties:- Under we know something about the distribution of .
- is relevant to the choice vs.

- The
*critical region*. A set of values that are used to reject the null hypothesis. In other words, the null hypothesis is rejected whenever the value we observe for is in .

- Model: 25 i.i.d. trials. At each trial we select a fish from the lake and test if it is toxic or not.
- :
- :
- : # number of toxic fish in our 25 fish sample.
- : .

2007-05-04