Validity of Measurement Content Validity Face Validity Concurrent Validity Predictive Validity Construct Validity Thinking Critically About Everyday Information

An essential component of an operational definition is measurement. A simple and accurate definition of measurement is the assignment of numbers to a variable in which we are interested. These numbers will provide the raw material for our statistical analysis. Measurement is so common and taken for granted that we seldom ask why we measure things or worry about the different forms that measurement may take. It is often not sufficient to describe a runner as " fast, " a basketball player as " tall, " a wrestler as " strong, " or a baseball hitter as " good. " If coaches recruited potential team members on the basis of these imprecise words, they would have difficulty holding down a job. Coaches want to know how fast the runner runs the 100-yard dash or the mile. They want to know exactly how tall the basketball player is, the strength of the wrestler, the batting average of the hitter. Measurement is a way of refining our ordinary observations so that we can assign numerical values to our observations. It allows us to go beyond simply describing the presence or absence of an event or thing to specifying how much, how long, or how intense it is. With measurement, our observations become more accurate and more reliable. Precision is important in all areas of our lives, especially in the sciences and technologies, and we look for ways of increasing it. Here is an interesting classroom demonstration of the precision of numbers versus the precision of words Ask the class members to write down on a piece of paper what number the word " several " represents to them. Gather the responses and then plot them on the board. You will be surprised at the wide range of numbers represented by the word (it usually ranges from 2 to 7). How often have you been in an argument with a friend, only to find out after much debate that you are using key words in different ways? The argument is one of semantics rather than of issues. You defined the word one way, and your friend defined it a different way. This experience is more common among laypersons than among scientists, but it still occurs. Before the merits of an issue or a position can be discussed, there must be agreement about the meaning of the important terms. The same is true in …