7. history

Foundations of Quantitative Measurement

  • Variables in clinical psychology research:
    1. Cognitive
    2. Affective
    3. Behavioural
    4. Biological
    5. Social
  • Construct: Underlying psychological concept.
  • Measure: Indicator or way of observing a construct.
  • Operationalization: Process of going from construct to measure.
  • Construct is latent and inferred from measurement operations.
  • Converging operations: Using multiple indicators to measure constructs.
  • Reactivity of measurement: Participants' behavior changes due to being measured.

Measurement Sources and Approaches

  • Self-report: Attitude questionnaires, symptom checklists.
  • Observation: Behavioural observation, brain scan.
  • Qualitative: Qualitative interviews, diaries, journals, participant observation, projective tests.

Advantages of Quantitative Measurement

  1. Greater precision in measurement.
  2. Well-developed theory of reliability and validity.
  3. Established statistical methods for data analysis.
  4. Data can be easily summarized.
  5. Facilitates comparison across individuals.
  6. Fits well with hypothetico-deductive approaches.
  7. Sampling theory can be used to estimate generalizability.

Positivism

  • Focuses on observable facts.
  • Applies methods used in physical sciences to social sciences.
  • Emphasizes objectivity and value-free science.
  • Logical positivism restricts philosophical discourse to sensory experience.

Methodological Behaviourism

  • Focuses on observable behaviour.
  • Excludes inner factors like cognitions and emotions.

Criticisms of Positivism

  • Excludes psychological constructs related to human experience.
  • Linked to capitalism, potentially reducing everything to numbers.

Chronometric Methods

  • Reaction time (RT) increases with task complexity.
  • Hick-Hyman law: RT is linearly related to information extracted from the stimulus.

Donders’ Method of Subtraction

  • Reaction times (RT) are crucial for studying the organization of mental processes.
  • Tasks:
    • Task A: Simple detection task
    • Task B: Discrimination task
    • Task C: Go/no-go task
  • Assumptions: consecutive cognitive processes are strictly serial and independent of each other.

Additive Factors Logic

  • Mental processing stages and their organization can be determined from systematic statistical interactions obtained with a single task.
  • Additive effects indicate different processes; interactions suggest variables affect the same process.

Interpreting Reaction Time Differences

  • Observed RT effect might be driven by unknown factors.
  • Control conditions help exclude alternative explanations.

Descriptive Designs

  • Study phenomena without manipulating variables.
  • Uses descriptive statistics (percentages, means).
  • May lead to correlational designs.

Correlational Designs

  • Find out how variables are related.
  • Measure many variables for each participant to study relations between them.
  • Cross-sectional or longitudinal.
  • Methods: Correlation coefficients, multiple regression, factor analysis, structural equation modelling.

Correlation and Causation

  • Correlation does not equal causation.
  • Conditions for inferring causality:
    • Covariation
    • Precedence
    • Exclusion of Alternative Explanations
    • Logical Mechanism
  • Conceptualizing causality: Path analysis.
  • Issues in drawing causal conclusions:
    • Direct causality
    • Reverse causality
    • Spurious relationships
    • Mediating factors
    • Moderating factors

Experimental Designs

  • Manipulate independent variable; use control group.
  • Establish cause-effect relationships.
  • Forms: Factorial, repeated-measures.
  • Statistical techniques: ANOVA, t-tests.
  • Assess validity to determine the strength of experimental design.

Cook and Campbell’s Validity Analysis

  • Internal validity: Differences in the dependent variable are caused by the independent variable.
  • External validity: Results can be generalized to other tests.
  • Framework encompasses statistical conclusion and construct validity.
  • Potential weaknesses in research study are flaws and limitations.

Validity Type & Defining Question

  • Statistical conclusion: Is there an effect?
  • Internal: Is it causal?
  • Construct: What does it mean?
  • External: Does it generalize?

Nonrandomized Designs

  • One-group Posttest-Only Design (XO): Lacks sufficient evidence for causal inferences.
  • One-group Pretest-Posttest Design (O1 X O2): Risky for inferring causation.
  • Nonequivalent Groups Posttest-Only Design (NR X O NR O): Major threat is uncontrolled selection.
  • Nonequivalent Groups Pretest-Posttest Design (NR O X O NR O (Y) O): Mitigate uncontrolled selection with statistical methods.
  • Interrupted Time-Series Design (O1 O2 … O20 X O21 … O40): Requires careful monitoring for interfering events.

Randomized Designs

  • Random assignment eliminates selection bias.
  • Enables manipulation of a single variable and fulfillment of causality conditions.
  • Control and comparison groups isolate effects of key variables.
  • Internal validity is often prioritized over external validity.

Design Variations

  • Basic Pretest-Posttest Design: ROXO R O (Y) O.
  • Multiple levels: Adding more experimental or control groups.
  • Multi-factorial Designs: Incorporating more than one between-groups factor.
  • Repeated-measures Designs: Assessing the same individuals at multiple points in time.
  • Blocking Factors: Grouping participants based on individual differences before randomization.
  • Analysis of Covariance: Individual differences have a linear relationship with the outcome variable.
  • Ethical considerations and scientific value determine the choice of control group.

Limitations of Randomized Designs

  • Ethical constraints prevent randomization in studying negative experiences.
  • RCTs may be unnecessary or inappropriate for obvious interventions.
  • Design requirements can make RCTs unrepresentative of normal clinical practice.
  • RCTs do not account for patient choice and may be influenced by researcher allegiance.
  • Practical issues: Ensuring group equivalence, dealing with attrition, preventing condition leakage, obtaining staff cooperation.
  • RCTs are costly and time-consuming.