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Hypothesis Testing

Hypothesis Testing. Chapter 6. Steps for Conducting Scientific Research. Step 1: Formulate a hypothesis. Higher temperatures cause people to be more irritable. Step 4: Report the results. Step 2: Design a study. Step 3: Collect & analyze data. Study Design.

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Hypothesis Testing

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  1. Hypothesis Testing Chapter 6

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

  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 [70o-72o], moderate [80o-82o], or a high [90o-92o] 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. Sample Sample Sample Sampling from the Population Population

  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 During the experiment, how much did the assistant make you feel the following:

  8. Creating Scale Scores

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

  10. x = 4 s = .5 3 4 5 x = 2 s = .5 1 2 3 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)

  11. Did the Results Occur by Chance? The treatment effect + Between groups variance Within groups variance F-ratio = Within groups variance 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).

  12. Inferential Errors

  13. Presenting Tabular Results Table 1 Analysis of Variance for Irritation

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

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