Information, Education and Communication: Graphic Presentation


Graphic Presentation:

Graphic presentation enjoys numerous forms of expression ranging from the written word to the most abstract of drawings or statistical graphs. When expressed in other than the written word, it affords an important medium of expression which, in health education helps to clarify literally, verbally, or statistically presented health information. The purpose of this medium is to enliven and delineate information by presenting it in concise manner and in such form or pattern as will be helpful to understanding. While this medium may be used alone in advanced study in many fields, it is, more often than not, used in support of, or in clarification of, data that are otherwise presented.

The purpose of the chart is to provide a concise summary or to compare, to contrast, to suggest relationships, or otherwise to explain. It is not a substitute for data ; that is , it does not take the place. Thus it is a symbolic form which, while representative, is explanatory. It may vary in pattern from the simple to the complex depending upon its type, colour arrangement, and the amount of detail that it presents. Its value in health education, as in genera usage, is usually in direct proportion to its simplicity.

The graph is a chart form that is used to present statistical (quantitative) data and to present the relationships between variables. While the terms "chart form" and "graph" are at times used interchangeably, the fact that use of the graph is restricted to the presentation of numerical data sets this form apart from other graphic forms which, though enjoying broader scope as to presentation, are limited in their possibilities for presenting quantitative data. It is this distinctive function of the graph that tends to set it apart from the chart, although it remains a chart form. With the graph as with the chart, the simplest form that serves the intended purpose is usually productive of best results. This most certainly is the case in school usage at both the elementary and secondary grade levels.

Definitions of Graphs and Charts:

A graph or chart is an instrument to present statistical information in symbolic fashion. The chart is used to represent numerical data as well as material in abstract form. In addition a certain type of chart (eg. map chart) may be considered a picture of a portion of the earth's surface.

Historically speaking, graphs probably had their origin in pictures. Many old paintings and engravings represent saints and royalty in large figures with halos surrounding them whereas persons of less importance are represented in smaller size. In other words, a persons social status was conveyed to the reader by means of a graphical technique.

Advantages and Disadvantages of Graphic Presentation:

Advantages:

  1. Simplicity in reading the data : It is an efficient method of showing large numbers of observations.
  2. The results are more easily remembered. A visual impression is more permanent than sets of figures of words.
  3. Completeness in presentation. Complex relationships can be demonstrated easily and quickly so that the whole situation is presented simultaneously.
  4. Clarity and emphasis in presentation. By the use of colour and other devices, one can emphasize certain places. For example, a rising death rate might be pictured in red to bring out the aspect of danger involved.
  5. Popular appeal. One need not consult surveys or psychological test results to learn that the table of statistical data may be quickly skipped over but a lively chart will attract and a certain amount of learning.


Disadvantages:

  1. A sacrifice in precision. A graph can be used only to show large or crude variations in the date.
  2. Lack of flexibility in the event new combination of the data seem appropriate. This follows as a result of the first disadvantage and is one of the reasons why it may be advisable to present the original data in a table or text accompanying the graph.
  3. Distortion of the situation may result from the desire to oversimplify the material. This may be intentional or otherwise.
  4. Construction of a graph or chart may be difficult or costly. This should only apply , however, to large scale drawings which are employed as posters to educate the lay public or similar groups.


The Data or Tabular Chart:

The data chart is used to present data in summary or tabular fashion. It is , in fact, a table that brings together data that are arranged in such fashion as to simplify their interpretation or make possible their further delineation in chart or graph form. Indeed the preparation of a table or data chart is a necessary first step in the preparation of other more vivid and refined charts which will further speed interpretation and enhance understanding of the basic data.


The Time Chart:

The time chart is used to present data of chronological nature. Historical data are frequently presented in this manner as indicents occurring at differert times are shown in sequential arrangement. While having something in common with the data or tabular chart, this form restricts itself to treatment of the time element. Thus, public health progress may be shown as administrative emphases are placed on different phases or areas of public health activity. The same story might well require several hundred words in the telling. Such a chart may accomplish the purpose in concise yet complete and interesting manner through a combination of words and symbols. The concept of time as a faster in public health progress is thus more readily appreciated than would be the case in the reading or hearing of words only. The time rate table and the time bar chart are other forms of the time chart. While commonly used to illustrate industrial and commercial operations, these forms find limited, though effective, application in health education.

The Tree or Stream Chart:

This chart form is frequently used to illustrate biological studies and is readily adapted to use for depicting health program growth and development. In its simplest form, this chart may consist of the outline of a tree with the trunk and branches appropriately marked to indicate source or origin and growth and development of any kind, e.g. the "family tree". As such, it is sometimes described as a pictorial growth Chart. In comples form it may, through careful and detailed drawing, delineate the multiplicity of operations involved in the production and transportation of food, water, or medical supplies.

The Organization Chart:

The purpose of the organization chart is to depict the structure of an organization. It may be used to indicate the administrative or functional relationships of component parts of the structure. or both. The organization of a municipal, country, state, or federal official health agency is usually shown in this form of chart. It is one of the simplest of the chart forms and is commonly Used by health agencies in organizational planning.

The Flow Chart:

The flow chart or flow diagram is used to depict the movement or flow of functions, materials, or services of an organization, or to illustrate the directions of flow of interagency responsibilities. For example, the directions of flow of personnel responsibilities within a health agency or the functional relationships of voluntary agencies to the official health department may be depicted in this manner. The concept of these agencies as ancillary or complementary agencies to the official community health agency is readily enhanced for the student as he is enabled to trace flows of responsibility visually.

The qualities of the orgariization chart and the flow chart are sometimes combined to produce an organization and flow chart. Such a chart may serve the dual purpose of showing the manner of agency organization and the flow of functions or services from its component parts.

The Bar Chart or Graph:

The bar chart or graph is without doubt the most commonly seen of the many chart forms used in presenting the relationships between variables. Among its many, patterns are the simple bar and the compound, multiple, relative, and pictorial bars, all of which may be structured in either the vertical or horizontal planes. Vari-coloured and multi-coloured bars may be used depending upon the number of variables shown. In such usage, however, the careful selection and placement of colours in just a position is an important consideration in any case and particularly when these forms are used in conjunction with the teaching of elementary school children. Hatching may also be used to advantage in most bar chart forms; but in paper charts, this is time consuming activity which, if not carefully done, may result in optical illusions and resultant confusion rather than clarity. Both colouring and hatching are effective and are readily accomplished when the chalk board is ,used to present the bar chart or graph.

Bar chart or graph forms enjoy popular usage in health literature. Expecially is this the case when birth, death, or morbidity rates are under consideration since comparisons of birth and death rates, case incidence and fatality rates, or specific morbidity and mortality rates are readily visualized with the help of these graphic presentations.

Histogram or Column Diagram:

This is a graph on arithmetic paper for presenting data in frequency distributions. The height of each interval is indicated by a column. (The name is derived from its root, histo, meaning cell or frame.) There is no space between each column.

It should be used only when the data on the horizontal or x-axis are measured on an interval or ratio scale. If data have been grouped into intervals unequal in size (such as 0-4, 5-9, 10-14, 15-24 years of age), this type of graph is the one most suitable.

The percentage for the interval 25-34 years of age is actually 16.0 per cent, but since all the previous intervals were based upon units of five years, it was necessary to convert the percentage for the ten year interval by dividing it in half. Similarly for the interval 35-44 years of age. Note that the width of the last two columns is twice that of the five-year columns. In other words, the total area represents relative differences in the frequency distribution.

If the graph is one involving rates, such mortality or morbidity, the occurrence of unequal intervals does not require a histogram. The conversation to a common base for comparison purposes has already been accomplished in the obtain rate because the denominator takes this factor into account.

In construction of the histogram, it is preferable to convert frequencies in each interval into percentages. Thus, comparisons of the height of a column in one distribution are not influenced by the total numbers of observations and enable comparisons between histograms. It also overcomes the objection of divining the frequency of 1arger intervals into fractions of a unit. Do not use a male-break in the histogram for it is the heoght of each column which is being compared.

Component Band Chart:

A variation of the bar chart is extremely useful when two or more sets of percentages are to be compared by graphical means. When only one set of percentages from nomical scale data is under study for comparisons within the set, earlier discussion indicated preference for the pie chart. When there is more than one set, however, the comparison, between two pie charts is not easily made. In its place, a convenient graph is the component band chart.

In interpreting this graph, it should be observed that the source of local funds increased greatly (over two times its proportional share five years previously) and that this increase came mostly from a reduction in the use of state funds.

Pictorial Statistics:

This is popular variation of the bar chart. Instead of using a plain column, the length of the bar is composed of a series of small identifying symbols. Each symbol may be used to represent a fixed number of items. The number of items is determined by the variable being graphed and this in turn determines the length of the bar.

Some general rules in their construction are as follows:

  1. Use descriptive and suggestive symbols when possible. For public health work, some recommended symbols are figures of a man, woman, child, bed, wheel-chair, nurse, doctor, coffin, etc. (For a complete listing of all symbols see catalogue from pictograph corporation. No address is available, however, it may be out of business.
  2. There should be legend explaining the number of units for which each symbol stands. The number of units for which a symbol stands should be in round numbers, 5,10,25,50,100, etc. It is permissible to split a symbol into portions to show a number less than one unit.
  3. Represent differing amounts by varying the number of symbols instead of the size of the symbol, Distortion will result if the size of the symbol is changed.
  4. Each symbol should be the same size - called isotype. The space between symbols must also be constant.


The Line Graph:

The line graph, like the bar graph, finds ready application to the needs of health education. This graph makes possible the presentation of data with a high degree of accuracy. In fact, careful work and use of the proper coordinate paper make possible the exact reproduction of numerical data, a quality not given to all forms of graphic presentation. Since different types of lines may be used in tracing the data, two or more illustrations, may be presented on the same graph. However, the graph is easily over-burdened. The compilation of more than two or three records on the same graph is not advised.

This is expecially true if confusion is to be avoided when this graph form is used in the instruction of school children. The graph may be made attractive and distinctions made more clear when solid lines of different colours are used in place of solid and broken lines of the same colour. An accurately drawn grid and the careful placement of plotting points both on and between the scale divisions make possible the drawing of straight line segments or curves with accurate and artistic results that will prove attractive to pupils while contributing to the development of careful and precise work habits. Such a graph may be used to record the classroom temperature and humidity records; to illustrate annual food or milk production or consumption records; to compare the changing costs of medical or other health services; or to record the data from health experiments conducted in the classroom or laboratory.

The Pictorial Graph:

The pictorial graph, or pictograph, takes its name from the symbolic pictures or figures that it used in lieu of other forms of presentation.

Pictograph figure or picture symbols may be arranged in vertical or horizontal bar fashion, in circular or cluster fashion, or as single figures used to strengthen the concept of meaning or relationship of statistical data. As with other forms of graphic presentation, they are not intended to replace the written word, but to amplify or complement it. They range from simple stick figures to diagrams or full pictures of inanimate objects and, botanical, zoological, and anthropological forms. Thus diagrams or pictures of bicycles or automobiles may be used in instruction for safety and accident prevention; of battles of milk, or food items in the study of nutrition; and of plants, animals, or man in the study of heredity, communicable disease, community or public health, or health and medical economics. Such presentation is attractive and meaningful at all ages.

The Pie Chart or Graph:

This circular presentation enjoys general usage and is probably familier to all educational workers. Its purpose is to present percentage or fractional differences within a single geometric pattern. Its use as a mnemonic device aids in the retention of information. This is particularly true with children. The use of this form is effective in presenting quantitative data in an interesting and colourful manner in elementary grades as well as in the secondary school. When a single circle is used it is called a simple pie chart or diagram. When two or more concentric circles are used, it is described as a concentric pie. In the latter case, its possibilities are further enhanced, although the degree of abstraction is increased as circles are added, as the number of pie slices or sections is increased, and as a variety of the hatching styles are used in the same pie.

It must be emphasized that the pie diagram should not be used haphazardly. Since fraction or percentage differences are to be distinguished, numerical values must be clearly shown and superfluous words should not be allowed to clutter up the pie. Colour may be used to advantage for identifying one or more of the pie slices. This is particularly effective with children.

The pie chart or diagram has ready application in the teaching of nutrition, safety, community and public health, and health economics. It is a versatile chart form which adds interest to health studies and effectively supplements basic data.

Frequency polygon.

This is actually a type of graph which comes under the classification of the arithmetic scale line graph (see II, 4 A.) It is used, to present data in the form of frequency distribution. Thus, the information from class observations on height would appear as follows:

For each height interval, a dot is centered in the interval a dot is centered in the interval and placed at level corresponding to the number of persons found in that height interval. These points are then connected by a series of straight lines. (This produces a many-sided figure with many angles. Hence, the graph, derives its name).

This type of graph is the only one suitable if one wishes to compare two frequency Distributions. Even thought the size of the intervals may be unequal, (indicating, the histogram) When two (or more ) frequency distributions are to be compared the frequency polygon is needed. If the intervals are of unequal size, one must modify the level of the point which is plotted in Accordance with the rules for the histogram.

If more than one line is placed on a single graph, one can distinguish between the lines by colour, or making one of the lines broken, one solid, one dotted, etc. These different types of lines should be explained in a legend or key.

As in a histogram, the frequency polygon is best plotted when the data in the intervals of the frequency polygon is being employed is compare the shape of two frequency distributions, the use of percentages is mandatory. Since the two frequency distributions may have differing total numbers of observations, a valid comparison of the shapes of the frequency polygon can be made only when the vertical scale is in percentage form.

Some authors recommend that at each end the line be brought down to zero at the, middle of the adjoining intervals. This is to show that, the total area or percentages under the curve is equal to unity. In some cases where the frequency distribution has values starting at zero because of the scale of measurement, this creates a ridiculous situation and can be avoided by omitting these terminal lines.

Scatter Diagram.

This is a special type of graph often useful to the research worker in pointing out relationships or associations. These relationships, need not ,always be causal in nature.

For each community a dot was placed to indicate the average amount of prenetal care as well as its maternal mortality rate for that year. The pattern of the points indicates that an association or relationship probably does exist between these two factors. The question whether this relationship is causal or not can not be answered by this procedure.

How to use the charts:

  1. Construct or select charts that rate high on each at the following criteria:
    1. Is the material closely related to the topic to be discussed ?
    2. Is the material interesting?
    3. Is the material useful in attaining an objective of the program.?
    4. Can the material be understood?
  2. Make sure that the letters, figures, pictures and other material on the charts are large enough to be seen by all members of the group.
  3. Place charts at a height where they can be seen by every members of the audience.
  4. Make sure that all charts are accounted for and arranged in the right sequence.
  5. Check the lighting on the charts. Low footlighting is often best.
  6. Keep, the first page of the chart covered until readily to present it.


When presenting charts, the f ollowing suggestions should be kept in minds:

  1. Present all of the material on the chart before discussing the information on the page. This will give the learners an over view of the material on the page before discussing the parts..
  2. Use a pointer to indicate the item being presented.
  3. Stand at one side of chart; never block its view.
  4. Keep eyes on audience as much as possible. Glance at chart only briefly.
  5. Avoid too much leader talk. Try to get learners to think and to discuss.