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Chapter 4. Choosing a Research Design. Functions of Research Design. Two Major Activities Exploratory Classifying Behavior Identifying Important Variables Identifying Relation Between Variables and the Behavior. Hypothesis Testing

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chapter 4

Chapter 4

Choosing a Research Design

functions of research design
Functions of Research Design
  • Two Major Activities
    • Exploratory
      • Classifying Behavior
      • Identifying Important Variables
      • Identifying Relation Between Variables and the Behavior.
    • Hypothesis Testing
      • Consists of Evaluating potential explanations for the observed relationships.
      • Exploratory provides the data to develop explanations
relationship catagories
Relationship Catagories
  • Two broad catagories of relationships between variables and behavior are:
    • Causal
      • One variable directly or indirectly influences another.
      • May be unidirectional or bidirectional.
    • Correlational
      • Changes in one variable accompany changes in another (a relationship exists).
      • Covary- When one variable is associated with specific changes in another.
correlational research major features
Correlational Research: Major Features
  • No independent variables are manipulated
  • Two or more dependent variables are measured, and a relationship is established
  • Correlational relationships can be used for predictive purposes
    • A PREDICTOR VARIABLE (indep) can be used to predict the value of a CRITERION VARIABLE (depend)
correlational research major features1
Correlational Research: Major Features
  • Correlational research cannot be used to establish causal relationships among variables
    • THIRD VARIABLE PROBLEM
      • The possibility that correlational relationships may result from the action of an unobserved variable.
    • DIRECTIONALITY PROBLEM
      • The difficulty of knowing the direction of causality between two variables.
correlational research when is it used
Correlational Research: When Is It Used?
  • When gathering data in the early stages of research
  • When manipulating an independent variable is impossible or unethical
    • e.g. abuse
  • When you are relating two or more naturally occurring variables
    • e.g. college success
experimental research major features
Experimental Research: Major Features
  • An independent variable is manipulated (with at least two levels)
    • Treatment (conditions associated with each level of the variable)
  • A dependent variable is measured
  • The most basic experiment consists of an experimental and a control group
  • Control is exercised over extraneous variables either by holding them constant or by randomizing their effects across treatments
  • A causal relationship between the independent and dependent variables can be established
extraneous variables
Extraneous variables
  • Variables that may affect the behavior being investigated but are not of interest in the study.
    • If not controlled 1) difficult to detect effects of independent variable & 2) chance differences may be produced.
  • Two Controls
    • Hold them constant (assure all variables are kept at same level besides independent)
    • Randomize their effects across treatments (random assignment helps)
strength and limitations of experimental research
Strength and Limitations of Experimental Research
  • Strength
    • Identification of causal relationships among variables
      • Not possible with correlational research
  • Limitations
    • Can’t use experimental method if you cannot manipulate variables
    • Tight control over extraneous variables limits generality of results
      • Tradeoff exists between tight control and generality
internal validity
Internal Validity
  • INTERNAL VALIDITY is the degree to which your design tests what it was intended to test
    • In an experiment, internal validity means showing that variation in the dependent variable is caused only by variation in the independent variable
    • In correlational research, internal validity means that changes in the value of the criterion variable are solely related to changes in the value of the predictor variable
  • Internal validity is threatened by CONFOUNDING and EXTRANEOUS VARIABLES
  • Internal validity must be considered during the design phase of research
external validity
External Validity
  • EXTERNAL VALIDITY is the degree to which results generalize beyond your sample and research setting
  • External validity is threatened by the use of a highly controlled laboratory setting, restricted populations, pretests, demand characteristics, experimenter bias, and subject selection bias
  • Steps taken to increase internal validity may decrease external validity and vice versa
  • Internal validity may be more important in basic research; external validity, in applied research
research settings
Research Settings
  • The laboratory setting
    • Affords greatest control over extraneous variables
    • Simulations
      • Attempt to recreate the real world in the laboratory
      • Realism is an issue
        • Mundane realism: How well does a simulation mimic the real world event being simulated
        • Experimental realism: How engaging is the simulation for participants
  • The field setting
    • Study conducted in a real world environment
      • Field experiment: Manipulate variables in the field
      • High degree of external validity, but internal validity may be low