If the results of a study are not deemed to be valid then they are meaningless to our study. If it does not measure what we want it to measure then the results cannot be used to answer the research question, which is the main aim of the study. These results cannot then be used to generalise any findings and become a waste of time and effort. It is important to remember that just because a study is valid in one instance it does not mean that it is valid for measuring something else.