Reliability vs. Validity
September 26, 2011
There’s only one way to find out…
Many people may argue that it is more important to have reliable results rather than valid results, and some may disagree. Or is it more important to have a good balance between the two?
Results are considered to be reliable if consistent results are collected from consistent conditions in an experiment. Achieving reliability can be considered easier than achieving validity as reliability is mostly a result of a well planned out experiment on behalf of the researchers. For example, most researchers can avoid achieving any extraneous variables that may affect the reliability of their results if they carefully plan and execute their research. This can be achieved if the researchers give the same instructions to each participant, that the researchers check that their equipment is working properly and fairly for each participant, and also any assistants used should be fully trained and prepared for the task. However many variables could still affect reliability, such as subject reliability. In observational studies, each researcher has to be fully briefed in detail of the criteria involved in the study. An example would be if a researcher was to look for ‘friendly’ behaviours or ‘aggressive’ behaviours, this must be consistent, as opinion may affect results if one researcher classes a behaviour as friendly and the other classes it as aggressive. Will this ever be fully achieved though? Is subjectivity too hard an issue to ever fully eliminate?
And in the other corner there is Validity. Validity is how appropriate the results are to what the researcher has claimed to have measured. Some may argue that Validity is more important as what would be the point in doing the research if you did not actually measure what you claim to have measured? Validity is not formed based on a single statistic, validity is formed based on a whole body of information. There are two types of validity; external and internal. Internal validity relates to the way in which the study has been conducted through its method and design, and also the extent to which the designers have considered alternative explanations for the results. External validity however relates to generalisability. Generalisability is the ability to apply the research findings to the rest of the target population, assuming based on the results that all members of this target group would achieve similar results. The issue with generalisability is whether or not research should be applied to the whole of the target population. It would be best to test each individual to get their own set of results, as the results gained from the experiment may not always be representative of the population as a whole. Can this ever be fully tested due to expenses and time constraints? Will our results ever be fully valid?
Overall reliability and validity are considered to be essential elements in psychological research, but whether one or the other is more important is questionable. Will we ever achieve fully reliable and valid results, or are there simply too many variables that will influence it?