STUDY DESIGN

Discuss possible study designs you might employ to research your question:     the reasons of obesity in the people in the United States of America and the ill effects of the same on the people
 The proposed research should not, in itself, be a literature review but a new study on a new group of study participants. Also, the design should be quantitative in nature.  Which of the designs described in Module 2 would you use to test your research hypothesis? What other designs could you also employ for this purpose? What would be the potential for bias in the study design/s you would use to test your hypothesis? After considering potential designs, state what the most appropriate design is. The following components must fit this particular design: sampling, variables, analysis, and limitations.

Identify 2-3 possible study designs that you could employ to address your research question and discuss the potential for bias with each of these. Select the most appropriate design for your study and provide rationale for your decision. Looking ahead...Ensure that sampling, variables, analyses, etc. will be compatible with this design. Develop and submit a 2-3 page paper in which these details are presented.

Overview of Study Designs
The study design is the overall plan for collecting and analyzing data.
	The PURPOSE OF YOUR RESEARCH DESIGN is to ENSURE that you get the CORRECT answer to your research question. 
	The different types of material indexed in MEDLINE and other data bases are labeled in the pyramid diagram, with the least clinically relevant at the bottom and the most clinically relevant at the top. 
	The four layers above case reports and case series represent actual clinical research. 
	The layers below are least clinically relevant and can be useful as background resources. 
 Observational Study Designs and the Role of Epidemiology 
	Epidemiology studies the various factors influencing the occurrence, distribution, prevention, and control of disease, injury, and other health-related events in human populations. 
	Epidemiologists are most concerned with the validity of research studies (see below) and epidemiologic designs are the basis of public health research. Clinical trials are a particular form of epidemiologic design and are primarily used in medical research
Cohort Studies
	Studies following a group of people in which some are exposed to the factor of interest, to determine the association between that exposure and a specific outcome. 
	Click here for more on cohort studies.
Related terms: Incidence and Prevalence
Prevalence: quantifies the proportion of individuals in a population who have the disease at a specific instant and provides an estimate of the probability (risk) that an individual will have the disease at a specific point in time.
o	Incidence: quantifies the number of new cases of disease that develop in a population of individuals at risk during a specific time.
Case-Control Studies
	Studies in which the proportion of cases with a potential risk factor are compared to the proportion of controls (individuals without the disease) in terms of that risk factor. 
	These studies are commonly used for initial, inexpensive evaluation of risk factors and are particularly useful for rare conditions or for risk factors with long induction periods. Due to the potential for many forms of bias, case control studies provide relatively weak empirical evidence even when properly executed. Nested case-control studies (case control studies within a cohort with exposure likely recorded before outcome) are more valid than "true" case-control studies. 
	Click here for more on case-control studies.
Cross-Sectional (Prevalence Study) Study
	A descriptive study of the relationship between diseases and other factors at one point in time in a defined population. 
	Click here for more on cross-sectional studies.
Ecologic Studies
	An observational analytical study based on aggregated secondary data. Aggregate data on risk factors and disease prevalence from different population groups are compared to identify associations. 
	Because all data are aggregate at the group level, relationships at the individual level cannot be empirically determined but are rather inferred from the group level. Thus, because of the likelihood of an ecologic fallacy, this type of study provides WEAK empirical evidence.