The Main Sources Of Systematic Error Discussion Paper
a. List and define the three main sources of systematic error (bias) in epidemiologic studies. b. What is the definition of a confounder? c. What are the 3 main characteristics of a confounder? d. What are the main approaches to dealing with confounding through both study design and data analysis? Study Design: 1) 2) 3) Data Analysis: 1) 2)
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Bias is also called as a systemic error , if an error occurs randomly then that is called as sampling error .
Systemic error will occur no matter how good the studies are.
There are many types of Bias known which are given below.
1. Observer bias : It is the error which occurs due to observer eg error by a doctor or by a nurse.
2. Interviewer bias : it is the error which is done by the interviewer eg if he asks a leading question to the cases it can produce this kind of error.
3. Experimental error: it occurs when a different instruments or tools are used in different study groups which has to be later compares. The Main Sources Of Systematic Error Discussion Paper
Other types of bias are as:
It is defined as that variable which is associated with the risk factor of a disease as well as the disease it self.
A confounder can be :
1. Direct: it is the factor which is directly a risk factor.
2. Indirect: A factor which is not related to the disease is helping this confounding factor to act on the disease.
3. Spurious: this factor does not cause the disease.
How to deal with confounding:
Prevention of confounding: It can be prevented by doing:
Randomisation removes the selection bias but most commonly stratification is done to remove a bias.
1. Observational studies: it includes Descriptive and analytical study design . In analytical study design we have Cohorts study and case controlled study.
2. Experimental studies: it includes non randomized and randomized controlled trials.
Bias is a systemic error which are of many types like observer bias , experimental bias , selection bias , interviewer bias etc
Confounder is a factor which is related to both risk factor as well as diseases.
Confounding is removed by stratification mostly. The Main Sources Of Systematic Error Discussion Paper