







Strength of Evidence Transferability Editor's Comments |
What are validity and reliability?One of the main functions of the research design is to ensure the highest possible quality of the data and this involves considering validity and reliability. The design of the research tools impacts significantly on the extent to which the data is valid and reliable. There has been extensive debate over the extent to which the terms validity and reliability can be applied within a qualitative context. Consequently alternative terms have been suggested by some qualitative researchers:
However Newby (2014) advocates the use of the terms validity and reliability within qualitative research, where a process of triangulation enables validity and reliability to be achieved. This Guide will also use the terms validity and reliability within qualitative contexts. Understanding validity In order to understand the possible factors influencing the validity of your findings, it is necessary to consider the different types of validity. To help you with this some of main types of validity have been explored in this MESHGuide (adapted from Cohen, et al., 2011). Internal validity This is concerned with the extent to which the data can be considered to support the conclusions which have been drawn from the data i.e. its plausibility and credibility. In qualitative research internal validity can be improved through:
External validity This relates to the extent of the generalizability of the data to other contexts. External validity within qualitative research are influenced by:
This type of validity relates to the researcher’s understanding of factors to be researched within the project, which are termed constructs. This will influence the way in which the researcher operationalizes these constructs and it is this which will impact on the validity of the findings. Ecological validity The nature of qualitative research requires that the setting in which the research is carried out should be as natural as possible. This contrasts with quantitative research, which relies on variables being identified and controlled in order to be able to investigate the impact that different variables have on one another. Two aspects need to be considered in relation to ecological validity:
The importance of ecological validity is illustrated in a project designed to establish the levels of anxiety the children were experiencing when engaged in science activities. The first pilot was carried out in a classroom where the researcher was unknown to the children. In her evaluation of the pilot the researcher identified this as a factor which was in itself influencing the children’s reactions within the activities and could even have impacted on their anxiety levels. This type of researcher effect has been termed the Hawthorne effect, where the research process is having an impact on the reactions or responses of the participants. Understanding reliability In qualitative research, reliability can be thought of in terms of the extent to which the data collected actually represents what is happening in the context being studied. Conversely in quantitative research the emphasis is on dependability, replicability and accuracy of the data. The table below compares reliability within qualitative and quantitative research contexts (Cohen, et al., 2011):
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