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Chapter 4

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

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  1. Chapter 4 Choosing a Research Design

  2. 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

  3. 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.

  4. 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)

  5. 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.

  6. 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

  7. 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

  8. 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)

  9. 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

  10. 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

  11. 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

  12. Factors Affecting Internal Validity

  13. Factors Affecting External Validity

  14. 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

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