Validity is the extent to which the instrument measure the variable to what it intended to measure.
I feel that validity is important because without it the research seems pointless, if the experiment did not measure what they were supposed to, what is the point? The ultimate aim is to tell people what the study has found and what it means, the accuracy and the truth about the results all come from the validity. So if any other ambiguous factors or variables that are found, this would questioned the validity of the research itself.
There are several methods for assessing the validity of measurement (Gravetter & Forzano, 2009). One of the example is called face validity which shows that when a measure (superficially) appears to measure what it claims to measure (this is the least scientific one, but simple as) said by Anastasi (1988). This can be demonstrated via the IQ test that we did for our Personality and Intelligence module, the questions included logic, reasoning, such questions appear to be appropriate for measuring intelligence which means that it has high face validity.
The relationship between validity and reliability, both are required in order to carry out quality measurement procedure, they can be independent and related. The two factors are linked together because a research cannot be valid unless it is reliable. Lets use the IQ test again to explain my point, if I was to do the IQ test twice and results came out to have a huge discrepancy (82 & 139), we would have no idea what my actual IQ is. This big gap between the results is very very unlikely, almost impossible if we are truly measuring intelligence, so I can assume that there during the test, there must be error (random/measurement/experimenter) in which that the numbers have no meaning to us, I mean how do I know if we are actually measure intelligence when using the IQ test (to use methods to assess the validity of research, see above points). On the other hand it is not necessary for a measurement to be valid for it to be reliable. An example would be your weight claims to be a measure of your IQ, although, there is no validity, it would be classified as reliable, producing steady scores from one measurement to another. – Just because something that is reliable does not mean it is valid. Just because something that is valid does not mean it will be reliable.
Validity should represent what the researcher tested, and should be strong in terms of that the content validity is high; clearly showing that what you have tested represents your field of study. All aspects of the research must be looked over as to how methods could invalidate findings, so no doubts are being questioned. Overall, Validity and reliability should work in hand in hand, validity alone is not nearly as strong as them two being used together.