Texas Instruments TI-92 Owners Manual - Page 287

Using Frequencies and Categories To manipulate the way in which data points are analyzed, you can use frequency values and/or category values. Frequency values let you "weight" particular data points. Category values let you analyze a subset of the data points. Example of a Frequency Column In a data variable, you can use any column in the Data/Matrix Editor to specify a frequency value (or weight) for the data points on each row. A frequency value must be an integer , 0 if Calculation Type = OneVar or MedMed or if Plot Type = Box Plot. For other statistical calculations or plots, the frequency value can be any number , 0. For example, suppose you enter a student's test scores, where: ¦ The mid-semester exam is weighted twice as much as other tests. ¦ The final exam is weighted three times as much. In the Data/Matrix Editor, you can enter the test scores and frequency values in two columns. Test scores Frequency values c1 c2 Tip: A frequency value of 0 effectively removes the data point from analysis. 85 97 92 1 1 2 89 1 91 1 95 3 These c1 weighted scores 85 are equivalent to 97 the single column of scores listed to the right. 92 92 89 91 95 95 95 Frequency of 2 Frequency of 3 Note: You can also use frequency values from a list variable instead of a column. To use frequency values, specify the frequency column when you perform a statistical calculation or define a stat plot. For example: Example of a Category Column Set this to YES. Type the column number (or list name) that contains the frequency values. In a data variable, you can use any column to specify a category (or subset) value for the data points on each row. A category value can be any number. 270 Chapter 16: Statistics and Data Plots