This pattern of distribution is known as the normal curve and has a symmetrical bell-shaped appearance. The curve is illustrated in Figure 2. As you can see, a large number of individual cases cluster in the middle of the curve. The farther from the middle or average you go, the fewer the cases. In general, distributions of test scores follow the same normal curve pattern.
Most individuals get scores in the middle range.
Standard score distribution . There are two characteristics of a standard score distribution that are reported in test manuals. The most commonly used measure of central tendency is the mean or arithmetic average score. Test developers generally assign an arbitrary number to represent the mean standard score when they convert from raw scores to standard scores. Look at Figure 2.