Transforming Theory to Practice ??? Public Health Research

Why Public Health research is essential? To gather information to support planning and changing services for the better and to improve services. To build a picture of current services, i.e. a baseline. To encourage discussion on whether service changes are necessary.   Public Health Research / Selection Bias: Selection bias can result when the selection of subjects into a study leads to a result that is different if you had enrolled the entire target population. If one enrolled the entire population and collected accurate data on exposure and outcome, then one could compute the true measure of association. Surveys generally don't enrol the entire population; instead take samples. However, if sampling done in a fair way i.e. fair representative of the distribution of exposure and outcome in the overall population, then one can obtain an accurate estimate of the true association (assuming a large enough sample, so that random error is minimal. Types ·         Referral bias ·         Loss of follow up bias ·         Health workers Bias ·         Confounding by indication Information bias refers to bias arising from measurement error. Information bias is also referred to as observational bias and misclassification. The estimate of association can be biased if subjects are incorrectly categorized with respect to their exposure status or outcome. These errors are often referred to as misclassification. They can result in either non-differential or differential misclassification.  For exposure misclassification, the misclassification is nondifferential if it is unrelated to the occurrence or presence of disease; if the misclassification of exposure is different for those with and without disease, it is Similarly, misclassification of disease [outcome] is non-differential if it is unrelated to the exposure; otherwise, it is differential.