[EPIDEMIOLOGY_LECTURE] Threats to Validity

• "TWO GENERAL CRITERIOS OF RESEARCH DEGISNS"

  Internal Validity and External Validity
• "TWO GENERAL CRITERIOS OF RESEARCH DEGISNS"

  Internal Validity and External Validity
• Refers to the extent to which the changes observed in the dependent variables (DV) are caused by the internal validity (IV)

  Internal Validity
• Questions of interval validity cannot be answered positively unless the design provides adequate control of extraneous variables

  Internal Validity
• Essentially a problem of control.

  Internal Validity
• Anything that contributes to the control of a research design contributes to its internal validity.

  Internal Validity
• "THREATS TO INTERNAL VALIDITY"

  Specific events or conditions, other than the treatment, may occur between the 1st and 2nd measurements of the participants to produce changes in the DV.

  History
• "THREATS TO INTERNAL VALIDITY"

  Processes that operate within the participants simply as a function of the passage of time.

  Maturation
• "THREATS TO INTERNAL VALIDITY"

  Exposure to a pretest may affect participants’ performance on a 2nd test, regardless of the IV.

  Testing
• "THREATS TO INTERNAL VALIDITY"

  Changes in the measuring instruments, in the scorers, or in the observers used may produce changes in the obtained measures.

  Instrumentation
• "THREATS TO INTERNAL VALIDITY"

  If groups are selected on the basis of extreme scores, statistical regression may operate to produce an effect that could be mistakenly interpreted as an experimental effect.

  Regression
• "THREATS OF INTERNAL VALIDITY"

  Important differences may exist between the groups before the IV is applied.

  Differential Section of Participants
• "THREAT TO INTERNAL VALIDITY"

  Occurs when there is a differential loss of respondents from the comparison group.

  Experimental Mortality
• "CONTROLLING FOR THREATS TO INTERNAL VALIDITY"

  Match on as many variables as possible and then randomly assign one member of the pair to the IV-other goes to the control group.

  Randomized Matching
• "CONTROLLING FOR THREATS TO INTERNAL VALIDITY"

  Select samples that are as similar as possible on some extraneous variable (e.g., IQ and Age).

  Homogenous Selection
• "CONTROLLING FOR THREATS TO INTERNAL VALIDITY"

  Into the design: include the extraneous variable as one of the IVs examines (e.g., gender).

  Building Variables
• "CONTROLLING FOR THREATS TO INTERNAL VALIDITY"

  Removing portion of performance that is systematically related to an extraneous variable.

  Analysis of Covariance
• "CONTROLLING FOR THREATS TO INTERNAL VALIDITY"

  Participants are in each of the experimental conditions, one at a time.

  Using Participants as their own Controls
• Refers to generalizability or representativeness of the findings.

  External Validity
• Question addressed here is to what groups, settings, experimental variables, and measurement variables can these findings be generalized?

  External Validity
• "EXTERNAL VALIDITY QUESTION ADDRESSED"

  What group, settings, experimental variables, and measurement variables can these findings be generalized?
• "EXTERNAL VALIDITY QUESTION ADDRESSED"

  What group, settings, experimental variables, and measurement variables can these findings be generalized?
• "EXTERNAL VALIDITY QUESTION ADDRESSED"

  What group, settings, experimental variables, and measurement variables can these findings be generalized?
• "EXTERNAL VALIDITY QUESTION ADDRESSED"

  What group, settings, experimental variables, and measurement variables can these findings be generalized?
• "TYPES OF EXTERNAL VALIDITY"

  Identifying the population to which results may be generalizable.

  Population External Validity
• "TYPES OF EXTERNAL VALIDITY"

  Concerned with generalizing experimental effects to other environmental conditions (i.e., settings).

  Ecological External Validity
• "TYPES OF EXTERNAL VALIDITY"

  Concerned with how well the operational definitions and the experimental procedures represent the constructs of interest.

  External Validity of Operations