Reliability & Validitiy in Research

I hope you enjoyed these fun Santa facts, but have a think… 

Who measured the stats, where did they come from?

Are the findings valid and reliable?? (Ok, probably not as these stats are about an old man in a big red suit from the North Pole..)


Validity refers to whether or not the study is actually measuring what it is intending to measure (Field, 2009). Reaction time is a good example of a valid instrument of measurement, as reaction time intends to measure the time it takes a person to react, and it does exactly this! It would be useless to use a measurement of say an IQ test to try and measure the time it takes someone to react.

Two main types of validity to consider are: internal and external. Internal validity focuses on the researcher testing what they were meant to test, whereas external validity focuses on whether the findings can be generalized.

Other types of validity are:

construct validity introduced by Cronbach and Meehl (1955), construct validity focuses on the degree to which an instrument measures the variables being investigated.

content validity ensures that the method of measurement is reliable and actually measures what it’s supposed to measure.

face validity a type of content validity, ensures the instrument is suitable

predictive validity successful results from previous research predicts of the outcome of future experiments or tests.

*To ensure validity, instruments and methods used during research must first be reliable.*


The purpose of reliability is to show that any significant results found in a piece of research have not been found just by chance and they are more than a one-off finding. A reliable experiment is expected to produce the same results if the study is repeated by other researchers. If the experiment is constantly repeated and the results always appear to be different, the study cannot be considered reliable.

Reliablity and validity work together, if the study doesn’t measure what it is supposed to then the results cannot be accurate. And if the results cannot be accurate and reliable then the study cannot be valid.