10:832:335 Lecture Notes - Lecture 9: Arkansas Highway 1, Osteoarthritis, Confidence Interval
3 Apr 2017
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Document Summary
A study is said to have internal validity when there have been proper selection of study groups and a lack of error in measurement. Concerned with the appropriate measurement of exposure, outcome, and association between exposure and disease. External validity implies the ability to generalize beyond a set of observations to some universal statement. Poor precision: occurs when the factor being measured is not measured sharply. Sampling error: occurs when the sample selected is not representative of the target population. Increasing the sample size can reduce the likelihood of sampling error. The lack of agreement in results from time to time reflects random error inherent in the type of measurement procedure employed. Bias may be defined as any systematic error in an epidemiological study that results in an incorrect estimate of the association between exposure and risk of disease. Bias results from systematic errors in the research methodology.
