1. Hypothesis Testing Chapter 6

2. Steps for Conducting Scientific Research Step 1: Formulate a hypothesis Step 2: Design a study Step 3: Collect & analyze data Step 4: Report the results Higher temperatures cause people to be more irritable

3. Study Design This study will examine the effects of temperature on irritability. Subjects will be randomly assigned to one of three temperature conditions (low [70 o -72 o ], moderate [80 o - 82 o ], or a high [90 o -92 o ] temperature room). While in the room an assistant will irritate the subjects. Subjects will then complete an irritation scale.

4. Hypotheses The Study Hypothesis Ha:The amount of irritation subjects report will be significantly different among the three temperature conditions. The Null Hypothesis Ho:There will be no significant differences in the amount of irritation reported by the subjects among the three temperature conditions.

5. Sampling from the Population Population Sample

6. Operationalize and Measure Variables Independent Variable: Temperature  3 Conditions Low (70° - 72°)Condition #1 Medium (80° - 82°)Condition #2 High (90° - 92°)Condition #3 Dependent Variable: Irritation  Operationalized as ratings of irritation in response to assistant Scale included in Appendix of paper

7. Irritation Scale Not at All A Little BitModerately Quite a BitExtremely irritated or annoyed?12345 furiously angry?12345 mad?12345 so angry you felt like hitting the assistant? 12345 During the experiment, how much did the assistant make you feel the following:

8. Creating Scale Scores SubjectConditionItem 1Item 2Item 3Item 4 Mean Score 1334533.75 2223232.5 3112121.5 SubjectCondition Mean Irritation Score 133.75 222.5 311.5

9. Describing the Data x = 4 s =.5 34 5 Condition 3n = 15 x = 3 s =.5 234234 Condition 2n = 15 x = 2 s =.5 123123 Condition 1n = 15

10. Hypothesis Testing What could cause the difference in ratings between condition 1 and condition 3?  Chance error individual differences not evenly distributed  Confounds  The independent variable (treatment) x = 4 s =.5 34 5 x = 2 s =.5 123123

11. F-ratio Between groups varianceWithin groups variance + = The treatment effect Variation due to chance (error). Typically caused by individual differences in participants By controlling within-group variation, scientists can isolate the effects of the independent variable on the dependent variable (between-groups variance). Did the Results Occur by Chance?

12. Inferential Errors True state of affairs Chance is responsible Chance is not responsible Null hypothesis decision Fail to reject Correct “acceptance” Type II error RejectType I error Correct rejection

13. Presenting Tabular Results Table 1 Analysis of Variance for Irritation SourcedfSSMSFp Irritation(I)1640 25.41.001 S within group error 36942.61__

14. Presenting Graphic Results (F = 5.0, p <.05)