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Chapter 2: The Research Enterprise in Psychology. The Scientific Approach: A Search for Laws. Basic assumption: events are governed by some lawful order Goals: Measurement and description Understanding and prediction Application and control. Figure 2.1 Theory construction.

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the scientific approach a search for laws
The Scientific Approach:A Search for Laws
  • Basic assumption: events are governed by some lawful order
  • Goals:
    • Measurement and description
    • Understanding and prediction
    • Application and control
the scientific method terminology
The Scientific Method: Terminology
  • Operational definitions are used to clarify precisely what is meant by each variable. Example: Lower scores on the Beck Depression Inventory = lower levels of depression
  • Participants or subjects are the organisms whose behavior is systematically observed in a study
  • Data collection techniques allow for empirical observation and measurement
  • Statistics are used to analyze data and decide whether hypotheses were supported
the scientific method terminology1
The Scientific Method: Terminology
  • Findings are shared through reports at scientific meetings and in scientific journals – periodicals that publish technical and scholarly material
    • Advantages of the scientific method: clarity of communication and relative intolerance of error
  • Research methods: general strategies for conducting scientific studies
experimental research looking for causes
Experimental Research:Looking for Causes
  • Experiment = manipulation of one variable under controlled conditions so that resulting changes in another variable can be observed
    • Detection of cause-and-effect relationships
  • Independent variable (IV) = variable manipulated
  • Dependent variable (DV) = variable affected by manipulation
    • How does X affect Y?
    • X = Independent Variable, and Y = Dependent Variable
experimental and control groups the logic of the scientific method
Experimental and Control Groups:The Logic of the Scientific Method
  • Experimental group: group that receives the “treatment” (some change in the I.V.)
  • Control group: does not experience the change in the I.V.
    • Random assignment
    • Manipulate independent variable for one group only
    • Resulting differences in the two groups must be due to the independent variable
extraneous and confounding variables
Extraneous and confounding variables
  • Crime rate is associated with ice cream sales
  • Crime rate is associated with the number of churches per square mile
experimental designs variations
Experimental Designs: Variations
  • Expose a single group to two different conditions
    • Reduces extraneous variables
  • Manipulate more than one independent variable

- Allows for study of interactions between variables

  • Use more than one dependent variable

- Obtains a more complete picture of effect of the independent variable

strengths and weaknesses of experimental research
Strengths and Weaknessesof Experimental Research
  • Strengths:
    • conclusions about cause-and-effect can be drawn
  • Weaknesses:
    • artificial nature of experiments
    • ethical and practical issues
descriptive correlational methods looking for relationships
Descriptive/Correlational Methods:Looking for Relationships
  • Methods used when a researcher cannot manipulate the variables under study
    • Naturalistic observation
    • Case studies
    • Surveys
  • Allow researchers to describe patterns of behavior and discover links or associations between variables but cannot imply causation
statistics and research drawing conclusions
Statistics and Research:Drawing Conclusions
  • Statistics – using mathematics to organize, summarize, and interpret numerical data
    • Descriptive statistics: organizing and summarizing data
    • Inferential statistics: interpreting data and drawing conclusions
descriptive statistics measures of central tendency
Descriptive Statistics:Measures of Central Tendency
  • Measures of central tendency = typical or average score in a distribution
  • Mean: arithmetic average of scores
  • Median: score falling in the exact center
  • Mode: most frequently occurring score
    • Which most accurately depicts the typical?
descriptive statistics variability
Descriptive Statistics:Variability
  • Variability = how much scores vary from each other and from the mean
    • Standard deviation = numerical depiction of variability
      • High variability in data set = high standard deviation
      • Low variability in data set = low standard deviation
descriptive statistics correlation
Descriptive Statistics: Correlation
  • When two variables are related to each other, they are correlated.
  • Correlation = numerical index of degree of relationship
    • Correlation expressed as a number between 0 and 1
    • Can be positive or negative
    • Numbers closer to 1 (+ or -) indicate stronger relationship
correlation prediction not causation
Correlation:Prediction, Not Causation
  • Higher correlation coefficients = increased ability to predict one variable based on the other
    • SAT/ACT scores moderately correlated with first year college GPA
  • 2 variables may be highly correlated, but not causally related
    • Foot size and vocabulary positively correlated
    • Do larger feet cause larger vocabularies?
    • The third variable problem
inferential statistics interpreting data and drawing conclusions
Inferential Statistics:Interpreting Data and Drawing Conclusions
  • Hypothesis testing: do observed findings support the hypotheses?
    • Are findings real or due to chance?
  • Statistical significance = when the probability that the observed findings are due to chance is very low
    • Very low = less than 5 chances in 100/ .05 level
evaluating research methodological pitfalls
Evaluating Research:Methodological Pitfalls
  • Sampling bias: sample is not representative of the population
  • Placebo effects: the subject’s expectations lead them to experience change
evaluating research methodological pitfalls1
Evaluating Research:Methodological Pitfalls
  • Distortions in self-report data:
    • Social desirability bias: the tendency to give socially approved answers to questions about oneself.
  • Experimenter bias: the researcher’s expectations about the outcome of the study affect the outcome
    • the double-blind solution
population and sample
Population and Sample
  • Population: the larger collection of people from which a sample is drawn and that researchers want to generalize about.
  • Sample: the collection of subjects selected for observation in an empirical study
ethics in psychological research do the ends justify the means
Ethics in Psychological Research:Do the Ends Justify the Means?
  • The question of deception
  • The question of animal research
    • Controversy among psychologists and the public
  • Ethical standards for research: the American Psychological Association
    • Ensures both human and animal subjects are treated with dignity