3. Choosing the best study design
Study design
Learning outcomes:
Observational Studies
➔ Define cohort studies
➔ Distinguish between prospective and retrospective cohorts
➔ Explain the nested case-control design and strategy
➔ Describe the multiple-cohort design
➔ Define cross-sectional studies
➔ Explain why cross-sectional studies yield weaker evidence for causality than cohort studies
➔ Define case-control studies and their benefits and problems
➔ Describe case-crossover studies.
Randomized Blinded Trials
➔ Define randomized blinded trials
➔ Explain how to design RBTs
➔ Describe how to choose the intervention and control conditions
➔ Describe how to define outcomes and adverse effects
➔ Describe how to select participants
➔ Describe how to measure baseline and outcome variables
➔ Evaluate approaches to randomizing and blinding.
Studies of medical tests
Learning outcomes:
➔ Understand the definition of studies of medical tests and how these studies differ from therapeutic intervention trials or studies to assess causality
➔ Explain how to select subjects for a study of a medical test
➔ Understand how to measure reproducibility of a test including use of kappa and the coefficient of variation
➔ Define key metrics to use in studies that assess the accuracy of a diagnostic test including sensitivity, specificity, predictive value, ROC curves, and likelihood ratios
➔ Understand how to design studies of clinical prediction rules and the associated limitations and challenges with this design.
Enhancing causal inference
Learning outcomes:
➔ Describe cause-effect relationships and enumerate the four rival explanations
➔ Identify ways to minimize chance
➔ Discuss bias and identify ways to avoid bias
➔ Identify ways to make confounding less likely
➔ Offer several suggestions or strategies for incorporating opportunistic observational designs
➔ Explain how causal inference can be enhanced by positive evidence.
The methods: matching study designs to research questions
Learning outcomes:
➔ Why the methods section is the most important part
➔ How to report study methods accurately and fully
➔ How to report methods to minimise bias and confounding
➔ How to use reporting guidelines for different study types.
Subjects and variables
Learning outcomes:
➔ Define sample and population, and describe how sample and population inform all clinical
research
➔ Identify criteria for a target population
➔ Compare and contrast approaches to sampling
➔ Describe several strategies for recruiting a sample of subjects.
Sample size and power
Learning outcomes:
➔ List the steps for estimating sample size for an analytic study
➔ Explain other considerations in calculating sample size for analytic studies
➔ List the steps for estimating sample size for descriptive studies
➔ Identify strategies to minimize the required sample size
➔ Explain other strategies for estimating sample size when there is insufficient information
Statistics
Learning outcomes:
➔ Define and describe box models
➔ Define and describe standard error
➔ Define and describe p-values
➔ Define null hypothesis
➔ Select the appropriate statistical tests for your study.
Questionnaires and qualitative research
Learning outcomes:
➔ Describe steps an investigator can take to ensure that questionnaires and interviews are as valid and reproducible as possible
➔ Define open-ended questions and closed-ended questions and devise several examples of both types of questions
➔ Identify desirable question elements as well as pitfalls to avoid
➔ Design a one-page instrument that is easy to read, easy to understand, and suitable for data entry.