Defining Your Variables

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Defining Your Variables

• Psych 7
• January 23rd

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Announcements

• Last day to take part in Pretesting
• Friday, January 26th
• Dina lecturing on Thursday
• My office hours on Wednesday are cancelled
• Quiz 1 scores are now posted on website

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Outline

• Variables
• Conceptual vs. Operational Definitions
• Relationships between Variables
• Independent and Dependent Variables

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Variables

• An event or condition that the researcher
  observes, measures or plans to investigate that
  is likely to vary or change
• 3 General Categories
• Situational variables
• Response variables
• Participant variables

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How would you measure the following?

• Height
• Weight
• Hunger
• Maturity

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Conceptual vs. Operational Definitions

• Start with a construct
• e.g., prejudice
• Come up with a conceptual definition
• e.g., positive or negative feelings about a
  member of a particular group
• Then decide on an operational definition
• e.g., ratings of various social groups on feeling
  thermometer scales

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Conceptual vs. Operational Definitions, cont.

• What are possible operational definitions of the
  following concepts?
• Intelligence
• Attraction
• Anger

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Conceptual vs. Operational Definitions, cont.

• Researchers may start with the same conceptual
  definition but come up with very different
  operational definitions
• Example Liking
• Social Psychologist Ratings of another persons
  attractiveness
• Developmental Psychologist Number of times a
  child picks one toy vs. another
• Cognitive Psychologist The amount of activation
  in the orbitofrontal cortex when tasting one type
  of food vs. another

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Relationships between Variables

• Goal of research is often to determine how 2
  variables are related
• 4 Types of Relationships
• Positive linear relationship
• Negative linear relationship
• Curvilinear relationship
• No relationship

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Graphing the Relationship between Variables I
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Independent and Dependent Variables

• Independent Variable
• Dependent Variable
• Depends on the IV

Independent Variable
Dependent Variable
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Independent and Dependent Variables, cont.

• Identify the IVs and DVs in each of the following
  examples
• What are the levels of the IV in each example?

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Graphing the Relationship between Variables II
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Assignment 1

• Hypothesis and Operational Definitions Handout
• Assignments should be done on a computer, but the
  graphs may be drawn by hand.
• 15 points
• Due on Thursday, February 1st

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Assignment 1

• Hypothesis and Operational Definition Exercise
• Choose 3 out of the 4 possible hypotheses.
• Hypotheses
• 1. Jury decisions are influenced by the
  attractiveness of the defendant.
• 2. A pregnant woman's diet affects the birth
  weight of her baby.
• 3. Exercise is related to levels of stress.
• 4. Number of hours worked is related to the
  number of hours spent studying.

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Assignment 1

• Answer each of the following questions for each
  of the 3 hypotheses you selected.
• Questions
• 1. What type of relationship would you predict
  (positive linear, negative linear, and so on)? (1
  point)
• 2. Graph and label the relationship you predict.
  State a prediction based on the relationship
  shown by your graph. (2 points)
• 3. Which is the independent or "cause" variable
  and which is the dependent or "effect"  variable?
  (1 point)
• 4. State an operational definition for each
  variable. (1 point)

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Thursday

• Reliability, Validity, and Measurement
• Cozby, Chapter 5