This document discusses cross-sectional studies. It defines a cross-sectional study as an observational study that measures exposure and health outcomes in a population at a single point in time, providing a "snapshot" of prevalence. It describes key characteristics, including simultaneously collecting exposure and outcome data, estimating prevalence rather than incidence, and inability to determine temporal relationships between variables. The document outlines advantages as being quick and inexpensive but also limitations such as inability to establish causation.

1. Title:- Cross sectional study
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2. Study Design
 A study design is a plan for selecting study
subjects and for obtaining data about them.
A research design is the blueprint for
conducting a study that maximizes control
over factors that could interfere with the
validity of the findings.
There are different category of study types: -
descriptive studies, Analytical studies, and
Experimental studies.
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3. Diagrammatical representation Study design
Descriptive
Case report
survey
Case series
Analytical
Cohort
case-control
Cross-sectional
Laboratory
Field research
observational
Experimental
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4. Analytical study
Analytical studies are undertaken to test a
hypothesis and the association between an
exposure of interest and a particular outcome
hypothesis typically concerns whether a
certain exposure causes (or is associated with)
a certain outcome
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5.  Most frequent researches are done in the form of
observational studies.
Observational study can be
• Retrospective =outcome occurred before study
starts
• Prospective = no out come occurred before study
starts
It do not interfere with the phenomena under study,
only observe in a systematic and standardized
manner
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6. • In observational studies normally three types
of study design are used: -
• Cross-Sectional (prevalence study)
• Case-control (Compares diseased animals
(cases) with non-diseased animals (controls))
• Cohort Studies (Follow the groups through
time to determine if disease develops) Also
Called Incidence.
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7. Cross sectional study
What are cross-sectional studies?
Described as a “snapshot” of a population in a
certain point of time because exposure and
outcome are determined simultaneously for
each subject.
 It is an observational study.
 It is also called prevalence study.
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8. Diagrammatical representation of cross sectional
Study
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9. Con’t…
Cross-sectional study measure simultaneously
the exposure and health outcome in a given
population and in a given geographical area at
a certain time.
cross-sectional studies are very useful in
descriptive studies when used in studies that
are proposed to be analytical.
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10. Cross sectiontional con’t….
The aim of cross-sectional studies is to obtain
reliable data that make possible to generate,
robust conclusions, and create new hypotheses
that can be investigated with new research.
The main characteristic of cross-sectional
studies is that the observation of variable.
Whether they are cases, individuals, or other
types of data, is performed in a single moment.
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11. Prevalence of disease and exposure can be calculated by 2x2 table
Disease Non Disease
Exposed
Non exposed
 Prevalence of exposure in diseased compared to non-
diseased:
a/a+c vs b/b+d
• Prevalence of disease in exposed compared to non-
exposed:
a/a+b vs c/c+d
a b
c d
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12. Applications of cross-sectional studies
 They are usually conducted to estimate the prevalence of the
outcome of interest for a given population, commonly for the
purposes of public health planning.
 Appropriate for screening hypotheses because they require
relatively shorter time and fewer resources.
 Also used to understand the prevalence of various conditions,
treatments, services or other outcomes and the factors
associated with such outcomes.
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13. Advantages of cross-sectional studies
 Relatively inexpensive
 Takes little time to conduct(quick)
serve as a basis for calculating sample size in
the planning of future analytical research
 Can estimate prevalence of outcome of
interest because sample is usually taken from
the whole population.
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14. Advantage con’t…
 Many outcomes and risk factors can be assessed.
 Useful for public health planning, understanding
disease etiology and for the generation of hypotheses.
 There is no loss to follow-up.
 No risk to subjects
 Current records occasionally can be used
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15. Disadvantages of cross-sectional studies
Cannot tell us about causal relationships (only
correlation).
Temporal sequence of cause and effect cannot
necessarily be determined
Only suitable for chronic conditions occurring at a
moderate level in the population
 Unsuited to the study of rare diseases
Unsuited to the study of diseases of short duration
 Generalizability limited by sampled population
and population definition.
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16. Disadvatage con’t…
Sample size requirements may be very large
(especially when looking at rare outcomes or
exposures).
It evaluates prevalence rather than incidence
Potential for selection bias (systematic differences
between characteristics of the study population
and the target population from which it was
drawn)
 Most observational studies use data gathered from convenient
populations such as veterinary clinics, abattoirs and particular
farms (inference be made with great care)
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17. Conclusion
Cross-sectional studies :-
have their great use in descriptive studies
used for public health planning,
understanding disease etiology and for the
formulation of hypotheses.
 Relatively cheap observational studies and
can be conducted in a short time.
cannot be used to establish causal relationship
between exposure and outcomes.
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18. Comparison of cross-sectional with cohort study
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19. Summary of observational study
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