Quasi Experiments Overview

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Questions and Answers

What does regression to the mean imply about extreme outcomes over time?

  • They are influenced only by external variables.
  • They become more extreme due to consistent factors.
  • They get less extreme as random combinations of factors diminish. (correct)
  • They remain constant and do not change.

Which situation is a clear example of attrition threat?

  • Changes in results because of repeated testing.
  • Participants improving due to expectation.
  • Individuals consistently leaving the study over time. (correct)
  • Variations in measures used in the study.

How can testing and instrument threats affect internal validity?

  • They enhance the effectiveness of placebo treatments.
  • They are caused by external events unrelated to the study.
  • They lead to a placebo effect in participants.
  • They can cause participant behavior to change due to prior testing. (correct)

What is observer bias primarily concerned with in the context of a study?

<p>Who conducted the measurement and the study's level of blinding. (A)</p> Signup and view all the answers

Demand characteristics are best described as:

<p>When participants guess the study's purpose and alter their behavior. (D)</p> Signup and view all the answers

Which aspect enhances external validity in studies?

<p>Utilizing diverse real-world opportunities for research. (A)</p> Signup and view all the answers

In research, what is the primary concern of construct validity?

<p>The appropriateness of the variables measured and manipulated. (D)</p> Signup and view all the answers

What does statistical validity primarily evaluate in a study?

<p>The magnitude of the observed group differences. (A)</p> Signup and view all the answers

What is a key characteristic of a quasi-experiment?

<p>The inability to randomly assign participants to independent variable conditions (D)</p> Signup and view all the answers

In the context of quasi-experiments, what is meant by 'selection effects'?

<p>Differences in participant characteristics at different independent variable levels (C)</p> Signup and view all the answers

What does 'maturation threat' imply in a quasi-experimental design?

<p>Changes occurring naturally over time that could affect results (B)</p> Signup and view all the answers

Which of the following is an example of a nonequivalent control group interrupted time-series design?

<p>Examining suicide rates before and after a specific show aired (B)</p> Signup and view all the answers

Why are researchers limited in their ability to draw causal conclusions in quasi-experiments?

<p>There may be uncontrolled confounding variables affecting outcomes (D)</p> Signup and view all the answers

What risk is associated with external historical events during a study?

<p>Internal validity may be compromised due to uncontrolled variables (C)</p> Signup and view all the answers

In the context of the cosmetic surgery study, what does the term 'nonequivalent control group pretest/posttest design' refer to?

<p>Pre-existing groups are used to measure differences before and after an intervention (B)</p> Signup and view all the answers

What phenomenon explains why many participants accept default options in organ donation?

<p>Social pressure and perceived effortlessness of the default choice (D)</p> Signup and view all the answers

What is a primary concern when conducting quasi-experimental research?

<p>Internal validity can be threatened by various confounding factors (D)</p> Signup and view all the answers

Flashcards

Regression to the mean

When an extreme outcome is caused by a combination of random factors that are unlikely to happen again, resulting in less extreme results over time.

Attrition threat

Participants dropping out of a study over time, posing a threat to internal validity if the dropouts are systematic (e.g., only those who experience improvement leave).

Testing threat

A type of order effect where participants change as a result of being tested before. The repeated testing itself can influence the outcome.

Instrument threat

A threat to internal validity when the measuring instrument changes over time. This change can affect the study's findings.

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Observer bias

When the researcher's expectations or biases influence how they observe and interpret participants' behavior.

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Demand characteristics

When participants guess the study's purpose and alter their behavior accordingly, affecting the study's results.

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Placebo effect

When participants improve simply because they believe they're receiving an effective treatment, even if the treatment has no actual effect.

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Quasi-experiment

A study design that does not randomly assign participants to groups, often used when random assignment is impossible or unethical.

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Nonequivalent Control Group Interrupted Time-Series Design

A group in a quasi-experiment where participants are not randomly assigned, and are measured repeatedly before, during, and after an event that differs across groups.

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Default Option

An option or choice presented as the default, often chosen because it requires less effort.

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Nonequivalent Control Group Pretest/Posttest Design

A quasi-experimental design where groups are not randomly assigned, and are measured before and after a treatment or event.

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Internal Validity

The extent to which a study allows researchers to draw causal conclusions about relationships between variables.

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Selection Effect

A threat to internal validity where groups differ systematically before the treatment, due to non-random assignment.

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Design Confounds

A threat to internal validity where an uncontrolled variable systematically varies with the independent variable, confounding the results.

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History Threat

A threat to internal validity where an external event affects all participants at the same time as the treatment, making it difficult to isolate the treatment's effect.

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Interrupted Time-Series Design

Participants in a study are repeatedly measured on a dependent variable before, during, and after the event or treatment, to examine its impact.

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Study Notes

Quasi Experiments

  • Quasi experiments are similar to experiments but researchers lack full control
  • They may not be able to randomly assign participants to conditions
  • Researchers may rely on pre-existing groups or naturally occurring events

Examples of Quasi-Experiments

  • Organ Donation:
    • Opt-in (people choose to donate) vs. opt-out (people must actively decline) methods
    • Default options often influence decisions
  • Cosmetic Surgery:
    • Researchers studied self-esteem after surgery
    • Used a nonequivalent control group (participants not randomly assigned) to assess effectiveness
  • Shows and Suicide:
    • Researchers evaluated suicide rates before and after a popular show (time-series design)
    • Assessed impact of show content on suicide incidents

Internal Validity

  • The ability to draw causal conclusions from results
  • Researchers have limited control of independent variables in quasi-experiments

Threats to Internal Validity in Quasi-Experiments

  • Selection Effects: Participants in different groups may differ systematically before the study begins
  • Design Confounds: An uncontrolled variable influences the independent variable
  • Maturation: Participants change over time, independent from the treatment
  • History: External events influence the outcome
  • Regression to the Mean: Extreme scores tend to become less extreme over time
  • Attrition: Participants dropping out of a study
  • Testing: Participants may improve over repeated testing regardless of treatment
  • Instrumentation: Changes in measurement instruments may influence results
  • Observer Bias: Researchers' expectations might influence observations
  • Demand Characteristics: Participants adapt their behaviors based on study goals

Other Important Considerations

  • Placibo Effect: Participants improve due to belief in treatment effectiveness
  • External Validity: The ability to generalize findings to other situations and populations
  • Ethics: Researchers must consider ethical implications of quasi-experimental studies
  • Construct Validity: How well the study measures the intended variables
  • Statistical Validity: The importance of effect size in quasi-experiments
  • Quasi-independent Variables: These are measured rather than manipulated (e.g., age, gender)

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