Changes

==Validity==

==Validity==

As mentioned [[Populations and samples#Sampling strategies|earlier]], the '''validity''' of an estimate is a measure of how well it can be extrapolated to the population in question (or, in the case of ''external validity'', to other populations). Therefore, both selection and information biases will tend to reduce the validity of an estimate, which is of particular concern for any epidemiological study.

As mentioned [[Sampling strategies#Populations and samples|earlier]], the '''validity''' of an estimate is a measure of how well it can be extrapolated to the population in question (or, in the case of ''external validity'', to other populations). Therefore, both selection and information biases will tend to reduce the validity of an estimate, which is of particular concern for any epidemiological study.

==Selection bias==

==Selection bias==