Research Methodology & Design Flashcards

A researcher wants to determine the prevalence of post-treatment hyperpigmentation across a clinic's patient records from the past five years. Which study design is most suitable?

Answer: Retrospective cross-sectional study

A retrospective cross-sectional study examines existing records at a single point in time to estimate prevalence of a condition. It is efficient and cost-effective for describing how common an outcome is in a population without requiring prospective follow-up.

What is internal validity in a laser clinical study?

Answer: The extent to which the study design supports causal conclusions within the study population

Internal validity refers to how well a study is designed to rule out alternative explanations for observed effects, allowing causal inferences within the study sample. Threats to internal validity include selection bias, confounding, and measurement error.

Which sampling method involves dividing a population into subgroups and randomly selecting participants from each subgroup proportionally?

Answer: Stratified random sampling

Stratified random sampling divides the population into homogeneous subgroups (strata) such as skin type or age group, then randomly samples from each stratum. This ensures all subgroups are adequately represented, improving precision and reducing sampling error.

In a laser hair removal study, the Fitzpatrick skin type of each participant is recorded. What type of variable is Fitzpatrick skin type?

Answer: Ordinal categorical variable

Fitzpatrick skin type (I–VI) is an ordinal variable: the categories have a meaningful rank order (lighter to darker pigmentation) but the intervals between types are not assumed to be equal, making it an ordered categorical (ordinal) variable.

What is the primary function of an Institutional Review Board (IRB) in laser research?

Answer: To protect the rights and welfare of human research participants

An IRB (also called an ethics committee) reviews research protocols involving human subjects to ensure participants' rights, safety, and welfare are protected. IRB approval is required before human subjects research can begin.

A 95% confidence interval for mean hair reduction is reported as 45%–65%. How should this be interpreted?

Answer: We are 95% confident the true population mean hair reduction lies between 45% and 65%

A 95% confidence interval means that if the study were repeated many times, 95% of the calculated intervals would contain the true population parameter. It expresses the precision of the estimate, not the probability for individual patients.