Subscript and Summation Notation Single Subscript ... - Statpower

X 3X 3Single Subscript NotationSingle Subscript NotationX1212314X 3Single subscript notation extends naturallyto a situation where there are two or morelists. For example suppose a course has 4students, and they take two exams. The firstexam could be given the variable name X,the second Y, as in the table below. Chow’sscore on the second exam is observationY 2X 3Single Subscript NotationDouble Subscript NotationStudentSmithChowBenedettiAbdul87658392X85669097YUsing different variable names to stand for eachlist works well when there are only a few lists, butit can be awkward for at least two reasons.• In some cases the number of lists can become large.This arises quite frequently in some branches ofpsychology.• When general theoretical results are being developed,we often wish to express the notion of some operationbeing performed “over all of the lists.” It is difficult toexpress such ideas efficiently when each list isrepresented by a different letter, and the list of letters isin principle unlimited in size.