Outcome Designs
What design is illustrated by the symbols R → X O / R → O
Randomized Control Trial post-test only
Provide an example of history bias
An event, not related to the intervention, occurs and influences the outcomes.
For examples:
Competing intervention
Exposure to similar information provided through media
A political/social/community event
A natural disaster
Selection differences between the participants in the intervention and the comparison groups lead to differences in exposure or impact of historical events
This sampling method deliberately selects individuals who are unusual or different from the majority—such as people with exceptional success or failure—to gain deeper insight into a phenomenon.
Deviant case sampling
What is purposive sampling?
In qualitative research, participants are typically selected for their ability to provide rich, relevant, and diverse insights into the phenomenon of interest.
What is one advantage of using a closed-ended question instead of an open-ended one in a quantitative survey?
Closed-ended questions are easier to analyze statistically and ensure standardized responses across participants.
Define "Net effect"
A study net effect is the difference between an observed outcome and the outcome that is observed int he control group or that would have occurred for those same study participants had they not been exposed to the program.
Provide one example of measurement bias
Instrumentation: reliability of the instrument changes; bias associated with data collection methods (type of methods used, social desirability, recall bias)
Testing: when the same instrument is used multiple times, respondents' scores improve because they are able to recall information from the pretest
Researcher effects: quality of data collection changes due to interviewer fatigue/experience; interviewer age/style influence responses; different interviewers/observers for the control and experimental groups
What threat when experimental and control groups are not equivalent at baseline?
Selection bias
In qualitative research, what are codes
Short labels that identify key ideas or concepts in the data.
A researcher evaluating a school fitness program decides to use items from a CDC standardized survey to measure physical activity.
Give one advantage of this decision.
The instrument’s validity and reliability have been established, supporting trustworthy data and national comparability.
Limitation: The tool may not capture context-specific activities or cultural nuances relevant to the local population.
Why is random assignment considered a powerful tool for improving internal validity?
It minimizes preexisting group differences and controls for selection bias
In an evaluation using a first-come, first-served recruitment strategy, what internal validity threat is introduced?
Selection bias
Example of a Matching Variable other than "demographics"
Predisposition
Motivation
Pre-existing learning skills
This qualitative sampling strategy begins with a few participants who help the researcher identify additional people from their social networks.
Snowball sampling
Identify the problem with this survey question: “Do you think exercise and healthy eating improve health?”
It is double-barreled—asks about two behaviors in one question.
Name one strength and one limitation of the posttest-only RCT design.
Strength—controls for selection bias; Limitation—no pretest data to verify equivalence.
Explain the concept of maturation bias
A change occurs in participants as a result of maturation or passage of time (teens aging, and becoming better educated)
Consists of two groups and three waves of measurement.
A switching replication design
A public health researcher wants to understand community attitudes toward adolescent vaccination.
Why would they choose focus group discussions over surveys or individual interviews for this study?
Because FGDs provide insight into collective beliefs, social norms, and group dynamics that influence behaviors—helping researchers understand not just what people think, but how they shape each other’s opinions.
This type of survey allows respondents to complete it on their own — often online or on paper — without an interviewer present.
Name one advantage and one limitation of using this method.
Advantage: It’s cost-effective and ensures greater privacy.
Limitation: There’s no interviewer to clarify questions, which may lead to misunderstandings or missing data.
What is the Interrupted Time Series design
This quasi-experimental design examines outcomes measured at multiple time points before and after an intervention - it helps distinguish whether changes after the intervention reflect the program’s true effect or just normal trends or fluctuation patterns.
What is internal validity?
The degree to which observed changes can be attributed to the intervention rather than other factors.
Why is random assignment considered a powerful tool for improving internal validity?
It minimizes preexisting group differences and controls for selection bias.)
Name two strategies to ensure rigor and credibility in qualitative research.
Triangulation reflexivity and member checking
Recognize common pitfalls ( researcher bias, misinterpretation of participant meaning).
Explain the difference between statistical significance and practical significance
Statistical = unlikely due to chance; Practical = meaningful impact in real life