Odds ratio table

The odds ratio is used to measure the association between a factor and a trait in a case controlled study. 
1. An odds ratio >1 implies that the presence of the factor increases the probability of the existence of the trait.
2. An odds ratio <1 implies the opposite i.e. presence of factor inhibits presence  of trait. 
3. An odds ratio =1 implies no impact of the factor on the trait. 

University of Michigan - Ann Arbor

Sutton-Tyrrell, K. (1991). Assessing bias in case-control studies. *AHA Journals*. 22(7),  938-939 from [www.ahajournals.org/doi/pdf/10.1161/01.STR.22.7.938 .](https://www.ahajournals.org/doi/pdf/10.1161/01.STR.22.7.938 .) 

Assessing bias in case-control studies.

Determining the relationship between risk factors and diseases (trait).

Motivation of the study

Illustrate how improperly selected cases/controls can generate biases in the study. Explore types of Bias generated during clinical studies.

Purpose of Paper

The paper focusses on case control studies done in a clinical setting. Thus it expands on types of biases generated in this environment. 
The types elucidated are : 
1. Referral Bias
2. Ascertainment Bias
3. Berkson Bias
4. Hospital Control Bias

Types of Bias outlined in paper

Odds Ratio

Several key conclusions emerge regarding the assessment of bias in case-control studies. First, bias can mask true associations and form false ones, potentially invalidating research findings. Second, there is no universal method to identify all biases; rather, the process is intrinsic to the specific research problem and must be addressed during the study's design phase. Finally, case-control studies are especially susceptible to biases because errors can occur in the selection of either the cases or the controls, both of which can adversely impact or entirely invalidate a study.

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