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Experiment Basics: Variables

Experiment Basics: Variables. Psych 231: Research Methods in Psychology. Introduction. Background Literature Review Statement of purpose Specific hypotheses (at least at conceptual level). Body. Participants How many Where they were selected from

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Experiment Basics: Variables

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  1. Experiment Basics: Variables Psych 231: Research Methods in Psychology

  2. Introduction • Background • Literature Review • Statement of purpose • Specific hypotheses (at least at conceptual level) Body

  3. Participants • How many • Where they were selected from • Any special selection requirements • Details about those who didn’t complete the experiment • Methods (in enough detail that the reader can replicate the study) Body

  4. Design (optional) • Suggested if you have a complex experimental design, often combined with Materials or Procedure sections • Methods (in enough detail that the reader can replicate the study) • Participants Body

  5. Apparatus/Materials • Procedure • What did each participant do? • Other details, including the operational levels of your IV(s) and DV(s), counterbalancing, etc. • Methods (in enough detail that the reader can replicate the study) • Participants • Design Body

  6. Results • Verbal statement of results • Tables and figures • These get referred to in the text, but get put at the end of the manuscript • Statistical Outcomes • Means, standard deviations, t-tests, ANOVAs, correlations, etc. • state the results but don’t interpret them here Body

  7. Discussion - interpret the results • Relationship between purpose and results • Theoretical (or methodological) contribution • Implications • Future directions (optional) Body

  8. References • Author’s name • Year • Title of work • Publication information • Journal • Issue • Pages Adolescent Depression 29 References Barnett, P. A., & Gotlib, I. H. (1988). Psychosocial functioning and depression: Distinguishing among antecedents, concomitants, and consequences. Psychological Bulletin, 104. Beck, A. T. (1978). Beck Depression Inventory. San Antonio, TX: Psychological Corporation. Benoit, D., Vidovic, D., & Roman, J. (1991, April). Transmission of attachment across three generations. Paper presented at the Biennial Meeting of the Society for Research in Child Development. Benoit, D., Zeanah, C. H., & Barton, M. L. (1989). Maternal attachment disturbances in failure to thrive. Infant Mental Health Journal, 3, 185-202. Benoit, D., Zeanah, C. H., Boucher, C., & Minde, K. (1989). Sleep disorders in early childhood: Association with insecure maternal attachment. Journal of the American Academy of Child and Adolescent Psychiatry, 31, 86-93. When something odd comes up, don’t guess. Look it up! The rest

  9. Adolescent Depression 29 • References Adolescent Depression 29 References Barnett, P. A., & Gotlib, I. H. (1988). Psychosocial functioning and depression: Distinguishing among antecedents, concomitants, and consequences. Psychological Bulletin, 104. Beck, A. T. (1978). Beck Depression Inventory. San Antonio, TX: Psychological Corporation. Benoit, D., Vidovic, D., & Roman, J. (1991, April). Transmission of attachment across three generations. Paper presented at the Biennial Meeting of the Society for Research in Child Development. Benoit, D., Zeanah, C. H., & Barton, M. L. (1989). Maternal attachment disturbances in failure to thrive. Infant Mental Health Journal, 3, 185-202. Benoit, D., Zeanah, C. H., Boucher, C., & Minde, K. (1989). Sleep disorders in early childhood: Association with insecure maternal attachment. Journal of the American Academy of Child and Adolescent Psychiatry, 31, 86-93. Adolescent Depression 29 Author’s Notes This work was funded in part through a grant from the Center For Teaching and Illinois State University. The authors would Like to thank Jack Smith and Jill Doe and two reviewers for Their useful feedback. Adolescent Depression 29 Footnotes 1 It has been pointed out that the way in which we use the Term “attention” is different from how it has commonly been Used in earlier work on perceptual integration. 2 An alternative approach to this issue would be to use a Masked priming paradigm. We are currently investigating This potential in our laboratory. • Authors Notes • Footnotes • Tables • Figure Captions • Figures Adolescent Depression 29 Figure Captions Figure 1. Presents the condition means from Experiment 1 Figure 2. Presents the conditino means from Experiment 2 The rest

  10. Chapter 8 • These are used to supplement the text. • To make a point clearer for the reader. • Typically used for: • Patterns of results • The design • Examples of stimuli Figures and tables

  11. #1 Clarity - say what you want to say • Acknowledge the work of others (avoid plagiarism) • Active vs. passive voice (avoid passive) • Active: “Monroe and Coey (2003) hypothesized that speakers use to much passive voice …” • Passive: “It was hypothesized by Monroe and Coey (2003) that speakers use to much passive voice…” Checklist - things to watch for

  12. Avoid biased language • APA guidelines: • Accurate descriptions of individuals (e.g., Asian vs. Korean) • Be sensitive to labels (e.g., “Oriental”) • Appropriate use of headings • Correct citing and references • Good grammar Checklist - things to watch for

  13. You’ve got your theory. So you want to do an experiment?

  14. What behavior you want to examine • Identified what things (variables) you think affects that behavior • You’ve got your theory. So you want to do an experiment?

  15. You’ve got your theory. • Next you need to derive predictions from the theory. • These should be stated as hypotheses. • In terms of conceptual variables or constructs So you want to do an experiment?

  16. You’ve got your theory. • Next you need to derive predictions from the theory. • Now you need to design the experiment. • You need to operationalize your variables in terms of how they will be: • Controlled • Manipulated • Measured • Be aware of the underlying assumptions connecting your constructs to your operational variables So you want to do an experiment?

  17. Hypothesis: Eating candy with peanuts improve memory performance • How might we test this with an experiment? An example

  18. Characteristics of the psychological situations • Constants: have the same value for all individuals in the situation • Variables: have potentially different values for each individual in the situation • Constants: • M&Ms are eaten • Variables: • Type of M&M: peanut vs plain • Memory performance Constants vs. Variables

  19. Conceptual vs. Operational • Conceptual variables (constructs) are abstract theoretical entities • Operational variables are defined in terms within the experiment. They are concrete so that they can be measured or manipulated Conceptual Peanut candies Memory Operational Peanut M&Ms Memory test Underlying assumptions Variables

  20. Independent variables (explanatory) • Dependent variables (response) • Extraneous variables • Control variables • Random variables • Confound variables Variables

  21. The variables that are manipulated by the experimenter (sometimes called factors) • Each IV must have at least two levels • Remember the point of an experiment is comparison • Combination of all the levels of all of the IVs results in the different conditions in an experiment Independent Variables

  22. Factor A Condition 1 Condition 2 Factor A Cond 1 Cond 2 Cond 3 Factor B Cond 1 Cond 2 Cond 3 Factor A Cond 4 Cond 5 Cond 6 • 1 factor, 2 levels 1 factor, 3 levels 2 factors, 2 x 3 levels Independent Variables

  23. Methods of manipulation • Straightforward manipulations • Stimulus manipulation - different conditions use different stimuli • Instructional manipulation– different groups are given different instructions • Staged manipulations • Event manipulation– manipulate characteristics of the context, setting, etc. • Subject manipulations – there are (pre-existing mostly) differences between the subjects in the different conditions (leads to a quasi-experiment) Choosing your independent variable

  24. Peanut M&Ms Bottlecaps • What about our candy experiment? 1 IV: Candy type (3 levels) Choosing your independent variable

  25. The variables that are measured by the experimenter • They are “dependent” on the independent variables (if there is a relationship between the IV and DV as the hypothesis predicts). Dependent Variables

  26. How to measure your your construct: • Can the participant provide self-report? • Introspection – specially trained observers of their own thought processes, method fell out of favor in early 1900’s • Rating scales – strongly agree-agree-undecided-disagree-strongly disagree • Is the dependent variable directly observable? • Choice/decision (sometimes timed) • Is the dependent variable indirectly observable? • Physiological measures (e.g. GSR, heart rate) • Behavioral measures (e.g. speed, accuracy) Choosing your dependent variable

  27. Conceptual level:Memory • What about our candy experiment? • Operational level: Some kind of memory test • Memorize a list of words while eating the candy • Then 1 hour after study time, recall the list of words • Measure the accuracy of recall Choosing your dependent variable

  28. Control variables • Holding things constant - Controls for excessive random variability • Number of M&Ms consumed • Time of day test taken Extraneous Variables

  29. Random variables – may freely vary, to spread variability equally across all experimental conditions • Randomization • A procedures that assure that each level of an extraneous variable has an equal chance of occurring in all conditions of observation. • On average, the extraneous variable is not confounded with our manipulated variable. • What your participants ate before the • experiment Extraneous Variables

  30. Can you keep them constant? • Should you make them random variables? • Two things to watch out for: • Experimenter bias (expectancy effects) • the experimenter may influence the results (intentionally and unintentionally) • E.g., Clever Hans • One solution is to keep the experimenter “blind” as to what conditions are being tested • Demand characteristics – cues that allow the participants to figure out what the experiment is about, influencing how they behave Control your extraneous variable(s)

  31. Confound variables • Other variables, that haven’t been accounted for (manipulated, measured, randomized, controlled) that can impact changes in the dependent variable(s) Confound Variables

  32. Read chapters 3 & 5. • Bring your textbook and/or APA Publication Manual to lab (if you’ve got one) • Don’t forget your first journal summary is due this week in lab Next time

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