Assignment

It's easy to get confused by the concepts of test or measurement validity and reliability. They're both really important concepts in research, so let's look at them in closer detail. I'm going to use a silly, but hopefully memorable, example. Let's say you're doing a study about how two groups (let's say happy clowns and sad clowns) compare in their ability to parallel park. You select a sample of each kind of clown; you match them for age and driving experience. Now, you watch while each clown parks a little clown fire engine against a curb, in between two little clown PT cruisers. You measure each clown's parking ability by how far away from the curb they get the front and back ends of the little clown fire truck.

Measurement Reliability: This tells you whether your measure gives the same result every time when all the conditions are the same. So, are you using a little rubber band clown ruler, or are you using a regular plastic ruler? The regular plastic ruler is more reliable because it will measure the same distance the same way every time. The little rubber band clown ruler is less reliable because one time you might stretch it a bit more than the next time and you're likely to get a different measure every time even though nothing has really changed.

Measurement Validity: This tells you how accurate your measuring tool is. In our example, it tells you whether an inch on the measuring tool is a real inch. Are you using a big giant plastic clown ruler or are you using a regular plastic ruler that has been manufactured in strict compliance with the Office of Weights and Measures (OWM)? The regular plastic ruler is a more valid measure because an inch is truly an inch as defined by the OWM. The big giant plastic clown ruler is a less valid measure because with that big ol' thing, every so-called inch really equals 6 inches, according to the OWM.

By thinking about this example, you can also see that a measurement must have good reliability in order to have good validity. The little rubber band clown ruler can never be a valid measure because you never know exactly how stretched or slack you need to make it for it to be showing you an actual inch. If it doesn't give you the same measurement under the same conditions, there's no way you can know when it is giving an accurate measurement. Therefore, it does not have good validity.

Question:

Provide some other examples of measures with good/poor reliability and validity, and explain why? 100 words in APA format.