Validity and reliability--What's it all about? Part 1. Validity in quantitative studies.

Linda Shields PhD, FRCNA, Professor of Nursing, University of Limerick, Ireland This is one of a series of short papers on aspects of research by Alison Twycross and Linda Shields Just because a research study has been published in a journal does not mean that it is good research or that the results are applicable to your area of clinical practice. When reading a paper, it is necessary to consider the validity and reliability of the study being described. This and the next article in this series will define validity and reliability, and will explain how you can ascertain whether a quantitative research study is both valid and reliable. Validity means that a tool measures what it sets out to measure – for example, that a pain assessment tool measures pain intensity rather than anxiety. There are several measures of validity that provide evidence of the quality of a study. Internal and external validity relate to the overall study design. Internal validity relates to the extent to which the design of a research study is a good test of the hypothesis or is appropriate for the research question (Carter and Porter 2000). External validity, meanwhile, relates to whether or not research findings can be generalised beyond the immediate study sample and setting. Measures that are used to assess the validity of data collection tools are summarised in the box below (these are adapted from Knapp (1998), Carter and Porter (2000), Peat (2002)). When reading a research paper, you need to look for evidence that the researcher has addressed the validity and reliability of the data collection tools. This is usually discussed in the methodology section of the paper PN