Week 3

• What are the two broad categories of error associated with measurement?

  Random error and constant or systematic error
• How do random errors affect experimental results?


  They obscure the results
• What is the effect of constant errors on experimental results?


  They bias the results
• What are extraneous variables?


  Undesirable variables that add error to our experiments
• What is the aim of research design regarding extraneous variables?


  To eliminate or at least control their influence
• What does random allocation or counterbalancing achieve in experiments?


  It results in an even addition of error variance across levels of the IV
• What are confounding variables?


  Extraneous variables that disproportionately affect one level of the IV
• How do confounding variables threaten internal validity?


  They add constant/systematic error at the level of the IV
• What can confounding variables result in regarding the measurement of the DV?


  Measuring an effect of the IV on the DV when it is not present or no effect when it is present
• What should researchers ideally do about confounding variables?


  Eliminate them
• What are some methods to control for confounding variables?


  Random allocation, matching, counterbalancing, control group
• What are the sources of confounding variables categorized as?

  Selection, history, maturation, instrumentation
• What does selection bias result from?


  Bias resulting from the selection or assignment of participants to different levels of the IV
• What is history in the context of threats to internal validity?


  Uncontrolled events that take place between testing occasions
• What does maturation refer to in experimental contexts?


  Intrinsic changes in the characteristics of participants between different test occasions
• What does instrumentation refer to in the context of threats to internal validity?


  Changes in the sensitivity or reliability of measurement instruments during the study
• What is reactivity in the context of internal validity?


  Awareness that participants are being observed may alter their behavior
• What are demand characteristics?


  Artefacts that can arise when participants alter their behavior based on perceived expectations
• What is experimenter bias?


  When the experimenter's expectations influence the outcome of the study
• What are blind procedures?


  Methods used to counteract reactivity, such as single or double-blind designs
• What are the key concepts related to measurement error?

  • Random error
  • Constant or systematic error
  • Extraneous variables
  • Confounding variables
• What are the threats to internal validity?

  • Selection
  • History
  • Maturation
  • Instrumentation
  • Reactivity
• What do precision and accuracy refer to in psychological measurements?


  Precision refers to exactness, while accuracy refers to correctness
• What is reliability in the context of psychological measures?


  The extent to which a measure provides the same results under the same conditions
• What are extraneous variables?


  Undesirable variables that add error to experiments
• How do random errors and constant errors differ in their effects on results?


  Random errors obscure the results, while constant errors bias the results
• What is the aim of research design when it comes to extraneous variables?


  To eliminate or at least control the influence of extraneous variables
• What are the two broad categories of error associated with measurement?

  Random error and constant or systematic error
• What are the two broad categories of error associated with measurement?

  Random error and constant or systematic error
• How do random errors affect experimental results?


  They obscure the results
• What is the effect of constant errors on experimental results?


  They bias the results