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  2. External validity - Wikipedia

    en.wikipedia.org/wiki/External_validity

    An important variant of the external validity problem deals with selection bias, also known as sampling bias—that is, bias created when studies are conducted on non-representative samples of the intended population. For example, if a clinical trial is conducted on college students, an investigator may wish to know whether the results ...

  3. Selection bias - Wikipedia

    en.wikipedia.org/wiki/Selection_bias

    A distinction of sampling bias (albeit not a universally accepted one) is that it undermines the external validity of a test (the ability of its results to be generalized to the rest of the population), while selection bias mainly addresses internal validity for differences or similarities found in the sample at hand. In this sense, errors ...

  4. Sampling bias - Wikipedia

    en.wikipedia.org/wiki/Sampling_bias

    A distinction, albeit not universally accepted, of sampling bias is that it undermines the external validity of a test (the ability of its results to be generalized to the entire population), while selection bias mainly addresses internal validity for differences or similarities found in the sample at hand. In this sense, errors occurring in ...

  5. Validity (statistics) - Wikipedia

    en.wikipedia.org/wiki/Validity_(statistics)

    The validity of a measurement tool (for example, a test in education) is the degree to which the tool measures what it claims to measure. [3] Validity is based on the strength of a collection of different types of evidence (e.g. face validity, construct validity, etc.) described in greater detail below.

  6. Impact evaluation - Wikipedia

    en.wikipedia.org/wiki/Impact_evaluation

    There are five key principles relating to internal validity (study design) and external validity (generalizability) which rigorous impact evaluations should address: confounding factors, selection bias, spillover effects, contamination, and impact heterogeneity. [5]

  7. Bias (statistics) - Wikipedia

    en.wikipedia.org/wiki/Bias_(statistics)

    Detection bias occurs when a phenomenon is more likely to be observed for a particular set of study subjects. For instance, the syndemic involving obesity and diabetes may mean doctors are more likely to look for diabetes in obese patients than in thinner patients, leading to an inflation in diabetes among obese patients because of skewed detection efforts.

  8. Dying To Be Free - The Huffington Post

    projects.huffingtonpost.com/dying-to-be-free...

    The last image we have of Patrick Cagey is of his first moments as a free man. He has just walked out of a 30-day drug treatment center in Georgetown, Kentucky, dressed in gym clothes and carrying a Nike duffel bag.

  9. Field experiment - Wikipedia

    en.wikipedia.org/wiki/Field_experiment

    Field experiments offer researchers a way to test theories and answer questions with higher external validity because they simulate real-world occurrences. [6] Some researchers argue that field experiments are a better guard against potential bias and biased estimators. As well, field experiments can act as benchmarks for comparing ...