@inbook{1138253215, author={Leslie G. Portney and Mary P. Watkins}, title={Statistical Measures of Validity}, booktitle={Foundations of Clinical Research: Applications to Practice, 3e}, publisher={McGraw-Hill Education}, address={New York, NY}, year={2017}, url={fadavispt.mhmedical.com/content.aspx?aid=1138253215} }