# Stats: Type of Tests

This document will explain how to determine if the test is a left tail, right tail, or two-tail test.

The type of test is determined by the *Alternative Hypothesis* ( H_{1} )

## Left Tailed Test

H_{1}: parameter **<** value

Notice the inequality points to the left

Decision Rule: Reject H_{0} if t.s. < c.v.

## Right Tailed Test

H_{1}: parameter **>** value

Notice the inequality points to the right

Decision Rule: Reject H_{0} if t.s. > c.v.

## Two Tailed Test

H_{1}: parameter **not equal** value

Another way to write not equal is < or >

Notice the inequality points to both sides

Decision Rule: Reject H_{0} if t.s. < c.v. (left)
or t.s. > c.v. (right)

The decision rule can be summarized as follows:

Reject H_{0} if the test statistic falls in the critical region

(Reject H_{0} if the test statistic is more extreme than the critical value)

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