1. ANATOMY OF A QUANTITATIVE FREQUENCY TABLE Classes. The number of Classes is generally between 5 and 20. Here there are 7. Class Limits: The Lower Class Limit is the smallest value that can be in a class. Upper Class Limit is the largest value that can be in a class. Here, the class 90 - 99 has a lower class limit of 90 and an upper class limit of 99. Class Width: The Class Width is the difference between the Upper Boundary of one class and the Upper Boundary of the class above or below it. Here the class width is 89.5 – 79.5 = 10. Class Midpoint: The Midpoint of a class is determined by adding the Lower and Upper Boundaries and dividing by 2. Here, the midpoint would be (39.5 + 49.5)/2 = 44.5. Note that the first class has a lower boundary and the last class has an upper boundary. The Midpoint is also referred to as the Class Mark. Time Between Eruptions for Old Faithful Geyser Class Boundaries (or Cutpoints): The Lower Boundary is the value that separates one class from the class smaller than it. The Upper Boundary is the value that separates one class from the one larger than it. The Boundary between the class containing the values 60-69 and the class 70-79 is one-half way between, or 69.5. NOTE: The Lower Boundary of one class is the Upper boundary of the class smaller than it. A value falling exactly on a Boundary is placed in the higher class. So, for example a value of 69.5 would be counted in the 70-79 class. Boundaries are often not shown and may be replaced by Class Limits. + = Building a Quantitative Frequency Table: 1) Determine the number of Classes for the table. One approach is to review the data and identify the Maximum and Minimum values. Find the Range. Divide the range by the desired number of classes and round up, if necessary, to a convenient whole number. Second option would be to arbitrarily select a size for classes. Note that the class size in this table is 10. Think inclusive here, the values 40 – 49 are 10 numbers. See Class Limits and Boundaries. 2) In the first column note the variable and list the classes. 3) For the Frequency (f) column Tally (add up) the number of occurrences falling within a class and list it here. 4) The third column is usually contains either a Relative Frequency (rf), obtained by dividing the class frequency by the total number of values (e.g. 8/200 =.04) or it contains a Percentage, which is obtained by multiplying the relative frequency by 100. 5) Add a title and footnotes as appropriate. Make sure the measure, such as seconds or pounds, are noted. 6) Optional columns may include the Cumulative Frequency (cf), which is a running sum of the frequency column and the Cumulative Relative Frequency (crf), which sums the relative frequency column. These two columns are useful in determining amounts in the table larger than a single class. Note that these columns are not summed in the Total row. See also: Boundaries, Class Limits, Class Midpoint, Class Width. Title and other supporting infoTable Components: Classes of variable Time with measure noted (sec.) Total: Only sum the frequency and relative frequency (or %) columns. f: Frequency of values in class. cf: Cumulative Frequency rf: Relative Frequency crf: Cumulative Relative Frequency = +