Graphical Representation of Information

INTRODUCTION Diagrams are particularly effective as a way of conveying quite complex information. Presenting information visually is easy to understand, and enables broad distributions and trends to be taken in quickly.

GRAPHICAL REPRESENTA TION OF FREQUENCY DISTRIBUTIONS Tabulated frequency distributions are sometimes more readily understood if represented by a diagram. Graphs and charts are normally much superior to tables (especially lengthy complex tables) for showing general states and trends. The methods of presenting frequency distributions graphically are as follows: Frequency dot diagram Frequency bar chart Frequency polygon Histogram Ogive. Stem and leaf diagram

Frequency Dot Diagram This is a simple form of graphical representation for the frequency distribution of a discrete variable.

Frequency Bar Chart

Frequency Polygon

Histogram

The Ogive This is the name given to the graph of the cumulative frequency. It can be drawn in either the "less than" or the "or more" form, but the "less than" form is the usual one

Stem and Leaf Diagram In addition to providing a visual representation of the data, stem and leaf diagrams can also allow further analysis of the data as it is possible to obtain the original data points from the diagram (i.e. there is no loss of information). Similar to the histogram, a stem and leaf diagram is a way of grouping your original data into classes. Like the histogram, it provides a partial sorting of the original data to allow a visual identification of the distribution pattern of the data. Unlike the histogram, it provides extra detail regarding individual values. In a stem and leaf diagram, each data value is split into a stem and a leaf. The leaf is usually the last digit of the number and the other digits to the left of the leaf form the stem. The stem and leaf diagram is plotted by listing the first digits (i.e. the "stems") in a column (and sorted in numerical order), then listing the second digit (i.e. the "leaves") in a second column to the right of the appropriate "stem" (and again sorted in numerical order).

Separate each number into a stem and a leaf Separate each number into a stem and a leaf. Since these are two digit numbers, the tens digit is the stem and the units digit is the leaf (e.g. for the number 79, the stem is "7" and the leaf is "9") Next, group the numbers with the same stems (e.g. 79 and 77 are in the same group as both have a stem of 7). Then, list the stems in numerical order (in our example, the stems range from 5 to 8 as the lowest value is 50 and the highest value is 87) in a column.

In a second column list the leaves to the right of the appropriate stem values. If your leaf values are not in increasing order, order them now. Finally, add a title to your diagram

PICTOGRAMS Pictograms are the simplest method of presenting information visually. These diagrams are variously called "pictograms", "ideograms", or "picturegrams“.

PIE CHARTS Pie charts, known also as circular diagrams, are used to show the manner in which various components add up to a total. Like pictograms, they are only used to display very simple information to non-expert readers.

BAR CHARTS

SCATTER DIAGRAMS

GENERAL RULES FOR GRAPHICAL PRESENTATION

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