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Our “ more complex ” method

Our “ more complex ” method. 1. Collect data about current behavior 2a. Experimental group - Change the suspected cause 2b. Control group - Don ’ t change the suspected cause 3. Don ’ t change anything else 4. Collect data about subsequent behavior

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Our “ more complex ” method

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  1. Our “more complex” method 1. Collect data about current behavior 2a. Experimental group - Change the suspected cause 2b. Control group - Don’t change the suspected cause 3. Don’t change anything else 4. Collect data about subsequent behavior 5. Compare data collected before and after the change was made

  2. Experiments • The method that has been discussed thus far is referred to as an Experiment • Variations on this method are the primary ways that researchers try to establish that one thing causes something else to happen

  3. Independent Variables • The aspects of the study that vary across time or across groups are known as Independent Variables • This will also be referred to as the manipulation in a given study • The manipulation will have, at least, two levels (sometimes called conditions)

  4. Our experimental designs • Experimental group • Pre-Test, Verbal Training w/ Feedback, Post-Test • Control group • Pre-Test, Verbal Training w/o Feedback, Post-Test

  5. Our Independent Variables • Feedback • Two conditions, i.e., with and without feedback • Session • Three levels, i.e., Pre-Test, Training, Post-Test

  6. Kinds of Independent Variables • Between-Subjects • Each participant receives only one condition of the Independent Variable • Within-Subjects • Each participant receives every level of the Independent Variable

  7. Our Independent Variables • Between-Subjects • Feedback • Two conditions, i.e., with and without feedback • Within-Subjects • Session • Three levels, i.e., Pre-Test, Training, Post-Test

  8. Kinds of Independent Variables • Manipulated • The researcher has control of these Independent Variables and can change them • Subject • The researcher does not have control over these Independent Variables, i.e., cannot change them • This lack of control prevents a research from being able to establish whether or not the Independent Variable caused something to happen • Studies with Subject variables are referred to as Quasi-Experiments

  9. Our Independent Variables • Both of our Independent Variables (Feedback and Session) are Manipulated variables

  10. How many levels (conditions) should my IV have?

  11. Experiment 1 Tipping Attentiveness

  12. Experiment 2 Tipping Attentiveness

  13. Experiment 3 Tipping Attentiveness

  14. Experiment 4 Tipping Attentiveness

  15. Summary • Two studies showed that attentiveness does not affect tipping • One study showed that attentiveness helped tipping, while a different study showed that attentiveness hurt tipping • What would you conclude?

  16. Benefits of > 2 IV Levels Tipping Attentiveness

  17. Dependent Variables • The data that you collect, as part of the logical method described earlier, is known as the Dependent Variable

  18. Our Dependent Variable • Accuracy • | (Estimated Distance - Actual Distance) | • Notes • The estimated distance refers to verbal and active estimates of distance

  19. A different way to think about IVs and DVs

  20. Identifying IVs and DVs • What behavior do the researchers measure? • That is the Dependent Variable • What do the researchers think influences (affects) the behavior being measured? • That is the Independent Variable • What two (or more) elements make up the Independent Variable? • Those are the conditions or levels of the Independent Variable

  21. Types of IVs • Is the influence something that the researcher can control? • If yes, then it is a manipulated IV • If no, then it is a subject IV • Was the influence distributed across groups? • If yes, then it is a between-subjects IV • If no, then it is a within-subjects IV • What behavior do the researchers measure? • That is the DV • What do the researchers think influences (affects) the behavior being measured? • That is the IV • What two (or more) elements make up the Independent Variable? • Those are the conditions or levels of the IV

  22. Relations Between IV Types • Manipulated • Can be between-subjects or within-subjects • Subject • Can ONLY be between-subjects

  23. How do I know that I have a good measure?

  24. Do I have a good measure? • To answer this question, researchers have to assess the reliability and the validity of their measures • Both of these are qualities that you want in a measurement

  25. Do I have a good measure? • Reliability • Do you get the same measurements if you make the measurements again?

  26. Do I have a good measure? • There are two common ways to examine the reliability of a measure • Split-half • Correlate the two halves of the measurement device • Test-retest • Give the measure • Give it again at a later date (usually after a week or two, if the thing being measured is a trait) • Correlate the two scores

  27. Do I have a good measure? • Validity • Are you measuring what you think you are measuring? • Different ways to assess • Face Validity • Criterion Validity • Construct Validity

  28. An example … • Farmer & Sundberg (1986) developed a scale of boredom proneness, which I will use as an example of how people validate a new measure • Farmer, R., & Sundberg, N. D. (1986). Boredom proneness: The development and correlates of a new scale. Journal of Personality Assessment, 50, 4-17 • They examined the Face, Criterion, and Construct Validity of their new measurement device

  29. Do I have a good measure? • Face Validity • Does the measurement device appear to be measuring what you think you are measuring? • For example, asking someone directly about their level of anxiousness has more Face Validity than inferring it from the number of times that he/she gets up out of a seat

  30. Farmer & Sundberg (1986) • There is no formal assessment technique for face validity • In this case, you look at what questions are asked, e.g., “Frequently when I am working I find myself worrying about other things”, or “I am good at waiting patiently”

  31. Do I have a good measure? • Criterion Validity • Does the measurement device give similar results to other ways of assessing the topic? • For example, does your new schizophrenia scale correlate with ratings of schizophrenia made by trained professionals?

  32. Farmer & Sundberg (1986) • Farmer and Sundberg (1986) correlated their new measure with • Self-rating of general boredom and interest • Self-ratings of boredom and interest in a specific class • A measure of boredom susceptibility • A measure of boredom at work

  33. Do I have a good measure? • Construct Validity • Is the construct being measured unique and separate from other similar constructs? • For example, is mental workload really different from stress?

  34. Farmer & Sundberg (1986) • Farmer and Sundberg (1986) correlated their new measure with measures of • Depression • Hopelessness • Perceived effort • Loneliness • Experience seeking • Life satisfaction • Course grades

  35. Summary • The logic of establishing cause-and-effect • Independent Variables • Manipulated Variables • Subject Variables • Dependent Variables • Reliability • Validity

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