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24. Systematic confoundings as threats to internal validity

Lecture



Singling out any independent variable does not rule out the possibility that the basic process is affected by both random and non-randomly accompanying changes in other variables that are not part of the hypothesized relationship between the independent and dependent variables. These are confounding (extraneous) variables.

An extraneous variable is a variable that is not part of the experimental hypothesis but that, under experimental conditions, may either affect the basic process under study or become confounded with the independent or dependent variable, thereby distorting the form of the dependence being investigated.

The greatest threats to internal validity come from systematic and non-systematic confoundings with extraneous variables.

Internal validity is a criterion for evaluating the planning and conduct of a study that allows conclusions to be regarded as reliable specifically about the particular dependence (and not another) that is formulated in the experimental hypothesis.

Systematic confounding is a non-random confounding of the levels of the independent variable and the extraneous variable, in which a particular level of the independent variable is regularly combined with an active or inactive level of the extraneous variable, as a result of which one cannot conclude that the established experimental effect is due to the action of the independent variable rather than the extraneous variable.

Experimental control should include stabilizing other confounding variables or randomly varying them across levels in order to rule out a correlation between the independent variable and the extraneous variable.

Controlling confoundings of the independent variable with the extraneous variable is the main task of planning when developing experimental schemes.

Extraneous variables are usually controlled by stabilizing them, or by averaging out the influences they exert, or by other means that are typically dictated by the chosen experimental scheme (for example, this may be presenting the extraneous variable at all levels of the independent variable, as in the experiment with the monkeys).

Thus, the confounding (extraneous) variables – changes in variables not included in the hypothesized relationship between X and Y – must be controlled.

Bredenkamp's scheme:

  1. artifactual conclusion: X→ confounding variable →Y

  2. reliable conclusion (provided the third variable is controlled):

X →

X × confounding variable → Y

confounding variable →

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Lectures and tutorial on "Experimental psychology"

Terms: Experimental psychology

Psychological experiment
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Natural experiment
Experimental research in psychology
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1. The concept of the experiment as an active method of research. Experimentation in the broad and narrow sense of the word.
2. The psychological experiment and the natural-science experiment.
3. Norms in the structure of the experimental method.
4. Criteria of the objectivity of methods of psychological research.
5. Types of psychological hypotheses and the methods of research corresponding to them.
6. The three basic conditions for drawing a conclusion about a causal relationship. Requirements for the formulation of cause-and-effect hypotheses.
7. Levels of hypotheses tested in a psychological experiment; transitions between them.
8. Experimental control (as a condition for planning and conducting a psychological experiment); its types and means.
9. Types of confounding and forms of their control in a psychological experiment.
10. The conception of the experimental fact as the result of a decision.
11. The experimental method and the observation method in psychology.
12. Inductive laws. The place of induction in the experimental and qualitative methods in psychology.
13. The specificity of different types of psychological experiment.
14. Approaches to understanding the term "experimental planning". Substantive and formal planning.
15. Artefactual conclusions in psychological research.
16. Competing theories and the so-called third competing hypothesis.
17. Deductive inference by the modus tollens syllogism and the asymmetry of conclusions.
18. The thought experiment and mental models of experiments.
19. Classifications of experimental designs. Planning as the selection of designs.
20. Meta-analytic research in psychology.
21. Intra-individual schemes and their application (aims, sources of threats to validity, etc.).
22. The causal type of explanation and generalization. Reductionism in psychological explanations.
23. Requirements that must be met in order to draw reliable/valid conclusions.
24. Systematic confoundings as threats to internal validity
25. Sources and control of the unreliability of data. The relationship between reliability and validity.
26. Schemes of correlational research.
27. The relationship between external and internal validity in intra-individual and between-group schemes.
28. Between-group schemes. The main strategies for selecting and matching participants into groups.
29. Schemes for controlling accompanying confoundings.
30. Additional variables and additional variation in psychological research.
31. Quantitative experiments and quantitative laws in psychology.
32. The observation method in experimental psychology.
33. Types of empirical data in psychological research.
34. The specifics of experiments conducted for scientific and for practical purposes.
35. The «experimenter effect» and the problem of the identity of experimental conditions; Johnson's experiment.
36. The main quasi-experimental designs.
37. Complete and incomplete experimental designs.
38. Planning as a means of increasing the validity of an experiment.
39. The world of theories and psychological reality. The methodological approaches of Popper and Holzkamp.
40. Control of group composition in between-group designs. The problem of the representativeness of the subject and the sample.
41. Operationalization of variables, operational and construct validity
42. Artificial and field experiments in psychology
43. The specifics of the laboratory experiment in experimental psychology
44. Testing statistical hypotheses and its connection with the testing of experimental hypotheses.
45. Control over inference and types of generalization in psychological research.
46. Types of validity as applied to psychological research.
47. The demonstration experiment (study) and the conception of psychological law in Lewin's school
48. Cross-cultural research in psychology
49. The modeling approach in psychology
50. Factorial experiments and conceptions of the interaction of variables in experimental psychology
51. True and pre-experimental designs (according to Campbell) of research in experimental psychology
52. Types of variables and their confounds in a psychological experiment.
53. Types of representativeness; the connection between the notions of representativeness and validity.
54. Classifications of empirical methods in psychology
55. Analytical and graphical representation of the main result of action (MRA) of variables and their interactions
56. Variables and designs in correlational research.
57. Quantitative and qualitative data in the experiment and in other research methods.
58. Statistical decisions and formal planning of an experiment
59. The method of «double stimulation» in the transition to non-classical psychology
60. Special effects clarified by factorial designs. Factorial designs in the representation of non-experimental data.
61. The emergence and control of sequence effects
62. The problem of psychological explanation. The deductive-nomological model.
63. The multilevel experiment and cross-individual designs.
64. The longitudinal method in psychology; the cohort
65. The concept of method and technique in psychological research.
66. Functional control as a condition for planning and conducting a psychological experiment.
67. The relationship between the correlational and quasi-experimental approaches in psychology.
68. Qualitative research in psychology
69. Correlational data and structural modeling in experimental psychology
70. Population hypotheses and sample surveys
Psychological measurement, its types, the measurement scale for a psychological experiment
Experimental psychology and educational practice