Lecture 19: Intro to Study Design

Question 1

What is the overview of study design types?

Answer 1

Descriptive
-Case reports
-Case series
-Surveys

Analytical
-Observational
-Cross-sectional
-Cohort
-Case-control
-Experimental
-Randomized controlled trials (RCTs)

Question 2

What are descriptive studies?

Answer 2

-Provide into about the occurrence of a disease BUT with no attempt to investigate associations
-Describe, do not compare
-Useful for generating hypotheses
-3 types (case reports, case series, surveys)

Question 3

What are the 3 types of descriptive studies?

Answer 3

1. Case reports (usually for medical)
   -Describe rare condition/unusual cases (single)
2. Case series
   -Describe usual clinical course of a condition of interest
   -Describes a series of cases of patients with a particular outcome
3. Surveys
   -Collect info from individuals in a population but no comparison just describing

Question 4

What are analytical studies?

Answer 4

-Statistical analysis of epidemiological data to establish relationships b/w risk factors and the occurrence of a disease
-Make comparisons b/w groups
-Useful for hypothesis testing

Question 5

What are the 2 types of analytical studies?

Answer 5

1. Observational studies
   -researcher has no control over the allocation of subjects to the groups being compared
   -Exposed subjects already exist (they would have been exposed regardless of the study)
   -3 types
2. Experimental studies
   -Researcher randomly allocates subjects to the groups being compared
   -Researcher intervenes

Question 6

How do we know to use an experimental study or an observational study?

Answer 6

We can choose an observational study instead of an experimental study if:
-The exposure of interest is harmful or may endanger life (high doses of radiation, or mixing alcohol and caffeine)
-Its too expensive to administer the exposure
-The exposure is complex and hard to control (opportunistic infections in immunocompromised people)
-Not practical to administer exposure (ex effect of living at high altitudes on metabolism and telling people to move to high or low altitude

Question 7

What are the 3 types of analytical observational studies?

Answer 7

The main difference between the different types of observation study types is how participants are selected

1. Cross-sectional: select participants WITHOUT REGARD to exposure or disease status ( everyone)
2. Cohort: select (outcome-free) participants based on exposure status
3. Case-control: select participants based on disease status

Question 8

Why is it important to learn about study design?

Answer 8

-Good study design practices minimize systemic errors (ie selection, info, confounding biases)
-A well-designed study is more likely to have a valid conclusions
-An informed reader can assess whether the study was done properly

Question 9

What is a critical appraisal?

Answer 9

-Determine whether the study was designed appropriately, whether results are valid, if can be applied to other context

Proper term
-Systematic process used to identify the strengths and weaknesses of a research article in order to assess the usefulness and validity of research findings

Question 10

What are some tips on evaluating studies?

Answer 10

Methodological and non-methodological factors
-Methodological: study design, statistical analyses, addressing bias (how study conducted)
-Non-methodological: relevance, originality, conflicts of interest

-Lack of a “gold standard” for evaluating studies so tend to use standardized checklists

Question 11

What are the questions asked on the checklist in a critical appraisal?

Answer 11

1. Relevance?
2. Adds something new?
3. What is the research question?
4. Appropriate study design?
5. Addresses bias?
6. Performed as per methods stated?
7. Hypothesis stated?
8. Appropriate stats used?
9. Justified conclusions?
10. Conflicts of interest