Determine the number of Classes If the number of classes is too small lack of

# Determine the number of classes if the number of

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Determine the number of Classes If the number of classes is too small lack of detail too large some classes will be empty Group all of the n data into K number of classes General rule: K is the smallest whole number for which 2 K n In Examples 2.2 n = 65 For K = 6, 2 6 = 64, < n For K = 7, 2 7 = 128, > n So use K = 7 classes 100 Number of Classes In General Number of Classes Size of Data Set 2 1 ≤n<4 3 4≤n<8 4 8≤n<16 5 16≤n<32 6 32≤n<64 7 64≤n<128 8 128≤n<256 9 256≤n<528 10 528≤n<1056 Determine the Class Length Find the length of each class as the largest measurement minus the smallest divided by the number of classes found earlier (K) For Example 2.2, (29-10)/7 = 2.7143 Because payments measured in days, round to three days 102 Form Non-Overlapping Classes of Equal Width The classes start on the smallest value This is the lower limit of the first class The upper limit of the first class is smallest value + class length In the example, the first class starts at 10 days and goes up to 13 days The next class starts at this upper limit and goes up by class length And so on 103 Seven Non-Overlapping Classes Payment Time Example Class 1 10 days and less than 13 days Class 2 13 days and less than 16 days Class 3 16 days and less than 19 days Class 4 19 days and less than 22 days Class 5 22 days and less than 25 days Class 6 25 days and less than 28 days Class 7 28 days and less than 31 days Tally and Count the Number of Measurements in Each Class Class First 4 Tally Marks All 65 Tally Marks Frequency 10 < 13 ||| 3 13 < 16 |||| |||| |||| 14 16 < 19 || |||| |||| |||| |||| ||| 23 19 < 22 I |||| |||| || 12 22 < 25 | |||| ||| 8 25 < 28 |||| 4 28 < 31 | 1 Histogram Rectangles represent the classes The base represents the class length The height represents the frequency in a frequency histogram, or the relative frequency in a relative frequency histogram 106 