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The stem and leaf diagram is a more modern way of displaying data than the histogram. It is a depiction of the shape of the data using the actual numbers observed. Similar to the histogram, the stem and leaf gives the frequencies of categories of the variable, but it goes further than that and gives the actual values in each category.

The marks obtained in Programming in Semester 1 are depicted as a stem and leaf diagram using

stem(prog1)

which yields Fig. 3.13.

The decimal point is 1 digit(s) to the right of the | 1 | 2344 1 | 59 2 | 11 2 | 5556777889999 3 | 0113 3 | 6 4 | 00000000 4 | 6779 5 | 12223344 5 | 56679 6 | 0011123444 6 | 566777888999 7 | 0112344 7 | 5666666899 8 | 001112222334 8 | 5678899 9 | 0122 9 | 7778

FIGURE 3.13 A Stem and Leaf Diagram

From Fig. 3.13, we are able to see the individual observations, as well as the shape of the data as a whole. Notice that there are many marks of exactly 40, whereas just one student obtains a mark between 35 and 40. One wonders if this has anything to do with the fact that 40 is a pass, and that the examiner has been generous to borderline students. This point would go unnoticed with a histogram.