Cross sectional study

1. Journal
Club

2. Define
 Confounding factors
 Bias
 Validity
-Internal
-External
Terms

3. Define
 Population
 Sample
 Characteristics being studied
-standardized observation
-clearly defined
-Methods of data collection applies to
the sample/ participants
Cross-sectional Design

4. Define
 Population
 Sample
 Characteristics being studied
-standardized observation
-clearly defined
-Methods of data collection applies to
the sample/ participants
Cross-sectional Design

5. Exposed
Developed
outcome
No outcome
Exposed
Developed
outcome
No outcome
Sample
Exposed Unexposed
Cross-sectional Design

6. Odds Ratio
Diseased No Disease
Exposed a b
Unexposed c d
a/b
c/d
OR = ‫ـــــــــــــــ‬
OR = 1
OR > 1
OR < 1 ?

7. Odds Ratio
Diseased No Disease
Exposed 50 150
Unexposed 10 90
50/150
10/90
OR = ‫ـــــــــــــــ‬
a/b
‫ـــــــــــــــ‬
c/d
= 3=

8. Measurements
 Population-based surveys
 Estimate the prevalence
 Calculate the ORs
Cross-sectional Design

9. Strengths
 Fast/ inexpensive
 Useful before big studies (Cohorts)
 Public health
-Planning
-Monitoring
-Evaluation
Cross-sectional Design

10. Limitations
 1-time measurement of exposure
and outcome
 Prone to biases
 Prevalence depends on the
incidence of the disease and the
length of survival
Cross-sectional Design
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