Unit 4: Observational Study Design (Part 1)

Question 1

What are Descriptive Studies?

Answer 1

• collect information about the occurrence of a disease, but make NO attempt to establish an association between cause and effect.
• describe the “what” relative to the “who,” “where,” and “when,” which helps to understand the “why.”
• to count, sample, survey, and assess risk.

Question 2

What are Analytical Studies?

Answer 2

• investigate reasons for disease/death/event/productivity (i.e., determinants of a disease) to ultimately prevent and control health problems.
• describe the “why” relative to the “what,” “who,” “where,” and “when.”
• to use measures of association and statistical models.

Question 3

What are Observational studies?

Answer 3

watch a group of subjects and observe their exposure and outcome status.

Question 4

What are the three types of observational studies?

Answer 4

1. Cross-sectional study
2. Case-control study
3. Cohort study

Question 5

What is a Cohort study? How does it relate to one’s hypothesis?

Answer 5

• study subjects are chosen on the basis of exposure status.
• hypothesis testing

Question 6

Whta is a Case-control study? How does it relate to one’s hypothesis?

Answer 6

• study subjects are chosen on the basis of outcome status.
• hypothesis testing

Question 7

What is a Cross-sectional study? How does it relate to one’s hypothesis?

Answer 7

• study subjects are chosen without regard to exposure or outcome status.
• hypothesis generating.

Question 8

What are Experimental studies?

Answer 8

researchers randomly allocate subjects to the groups being compared, and play/sort a group of subjects and generally intervene.

Question 9

What are the two types of experimental studies?

Answer 9

1. laboratory trials
2. field trials

Question 10

What are the steps of a cross-sectional study?

Answer 10

1. Randomly sample individuals from the source population.
2. Take measurements (e.g. questionnaire, medical test, etc.) on each individual at one point in time to determine both Exposure (E) and Outcome (O) status: can collect information on multiple outcome and exposure variables.
3. Classify each individual on the basis of his or her E status (i.e. Exposure positive [E+] and Exposure negative [E-])
4. Classify each individual on the basis of his or her O status (i.e. Outcome positive [O+] and Outcome negative [O-])
5. Compare the prevalence or odds of disease in E+ and E- groups.

Question 11

What are the benefits of a cross-sectional study?

Answer 11

• determine the prevalence of E and O.
• fast and inexpensive.
• less potential for bias.
• good for studying permanent factors.
• can be used to assess associations between multiple E and O.
• can estimated almost all measures of association and effect.

Question 12

What are disadvantages of cross-sectional studies?

Answer 12

• Selection bias
• Information bias
• Confounding
• Measures prevalence, not incidence.
• Have major time issues (we aren’t able to definitively say whether the E really came before the O.)