MEDI251 Lecture Notes - Lecture 8: Confounding, Sampling Error, Observational Error
7 Aug 2018
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Document Summary
Describe sources of bias and ways to reduce them. Validity of study designs: two components of validity: External validity = generalizability: external validity implies the ability to generalize beyond a set of observations to some universal statement, can findings of study be expressed to a bigger group. Sources of error: random errors reflect fluctuations around a true value of a parameter because of sampling variability: factors contributing to random error, poor precision, sampling error, variability in measurement. Poor precision: occurs when the factor being measured is not measured sharply, analogous to aiming a rifle at a target that is not in focus, precision can be increased by increasing sample size or the number of measurement. 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 (statistical power to detect differences: random sample each member of population has equal chance being selected.
