So, does all this talk about validity and reliability mean you need to conduct statistical analyses on your classroom quizzes? No, it doesn't. (Although you may, on occasion, want to ask one of your peers to verify the content validity of your major assessments.) However, you should be aware of the basic tenets of validity and reliability as you construct your classroom assessments, and you should be able to help parents interpret scores for the standardized exams.
Another way to get more reliable results would be to use better measurement methods to show measurements more realistically . using lbs instead of stones. This allows us to see our weight in a better light. For example if we just uses stones it may show that every month we weigh the same but if we used lbs we may see, for example that we have been putting weight on.
I liked the way that you explained the 2 different types of validity and used an example that we can all relate to from having to do the IQ tests in Personality and Individual Differences. I also thought that it was good that you also had a study to use as evidence. It is always good to have evidence to support your statement and to explain how it benefits us now in real life.
I thought that your explanation about how a measurement cannot be valid unless it’s reliable but a measurement can be reliable without being valid was clear and explained the fact well.
Reliability and validity are, conceptually, quite distinct and there need not be any necessary relationship between the two. Be wary of statements which imply that a valid test or measure has to be reliable. Where the measurement emphasis is on relatively stable and enduring characteristics of people (. their creativity), a measure should be consistent over time (reliable). It also ought to distinguish between inventors and the rest of us if it is a valid measure of creativity. A measure of a characteristic which varies quite rapidly over time will not be reliable over time - if it is then we might doubt its validity. For example, a valid measure of suicide intention may not be particularly stable (reliable) over time though good at identifying those at risk of suicide.