1. Chapter 9: Hypothesis Testing
Section 1: Introduction to Hypothesis Testing

2. Example
A food company produces bags of peanuts weighing 336 grams (on the average). Periodically, the quality control department takes samples of peanut bags to determine whether the packaging process is under control.

3. = 336 g (process is under control)
≠ 336 g (process is not under control)

4. null hypothesis
a statement asserting no change, no difference, or no effect
value is often a historical value, claim, or production specification
usually takes the form of a statement about a population parameter
usually contains an equals sign
labeled Ho

5. alternate hypothesis
a statement that might be true instead of the null hypothesis
accepted when the null hypothesis is rejected
usually contains the symbols >, <, or ≠.
labeled H1

6. hypothesis testing procedure for choosing between hypotheses
gives the benefit of the doubt to the null hypothesis
the null hypothesis will be rejected (and alternate hypothesis accepted) only if sample data suggest beyond reasonable doubt that the null hypothesis is false

7. Steps in Hypothesis Testing
Identify the null hypothesis Ho and the alternate hypothesis H1.
Choose α, the level of significance.
Calculate the test statistic.
Determine the critical region.
Make your decision.

8. Types of Hypothesis Tests
Statement is
more than 100
less than 100
Different from 100
Equal to
Null Hypothesis Ho
=100
Alternate Hypothesis H1
>100
<100
≠100

9. Possible Decisions in a Hypothesis Test
Null Hypothesis
Decision
Reject Ho
Do Not Reject Ho
True
Type I Error
Correct Decision
False
Type II Error

10. Type I Error rejecting the null hypothesis when it is true
occurs if a test statistic falls in the critical region when Ho is actually true
probability of making a Type I error is called the level of significance, denoted

11. Type II Error not rejecting the null hypothesis when it is false
occurs if the test statistic does not fall in the critical region when Ho is false
probability of making a Type II error is denoted

12. Critical Region and Types of Test
H1: left-tailed test
H1: right-tailed test
H1: two-tailed test