Table 2: Raw data on 227 school children ‘s mathematical self-concept and mathematical achievement as presented originally for analysis

If you wish to refer to a single score from this set without specifying which one, you could can refer to xi, where i can take on any value between 1 and 5. The first score (5) would be referred to as x1, the second x2, and so on. A general form of notation for this example would be (xi; I=1, 2,…n). This means in the set of n values of the variable X, a single value xi may extend over a range of values from 1 to n.