CHART

From Big Medical Encyclopedia

CHART (grech, diagramma the drawing, the image) — the graphic representation demonstrating linear pieces or geometrical figures a ratio between various sizes.

Are widely applied in medicine, being means of the evident image of statistical materials, and have the following appointment: to facilitate and deepen the analysis of statistical data; to facilitate perception of statistical materials for the reader; to facilitate operational management of work, showing the course of implementation of the plan, dynamics of these or those aspects of medical service of the population, and also overall performance to lay down. - the prof. of institutions.

Charts happen linear, plane, dot, volume and figured.

Fig. 1. The linear dvukhordinatny chart displaying dynamics of incidence with temporary disability (in cases and days of disability on 100 working) at the plant N.
Fig. 2. The radial chart displaying seasonal spread of acute gastrointestinal diseases to areas N (a detailed explanation see in the text).
Fig. 3. The stylar chart displaying incidence with temporary disability (in cases of disability on 100 working) workers in mines.

Linear charts are applied to the image of the phenomena in dynamics. They are under construction on system of coordinates. On a horizontal axis (abscissae) intervals of time, and on a vertical axis (ordinates) — numerical values of the observed phenomena are postponed. In a point of intersection of these axes initial figures of counting, most often zero are put. But if the phenomenon of the zero size has no (e.g., temperature of a human body), then minimum possible initial phenomena are put.

As a rule, intervals of time (on abscissa axis) shall be equal unless the taken periods of observation are not identical. In the presence of two phenomena having sharply different sizes (e.g., number of days and cases of temporary disability due to illness on 100 workers), the so-called dvukhordinatny chart (fig. 1) is recommended, on one axis the cut is postponed scale for number of cases, and for another — the scale of number of days. It is not necessary to use linear charts for the image of structure of the phenomenon.

Radial charts are a kind of linear. They are applied to reflection of the phenomena (processes) having seasonal nature. In these cases, using absolute data on months, calculate previously average monthly size of the phenomenon for this year and take it for the full radius of a circle, length to-rogo conditionally is accepted for 100. At the same time if the size of the phenomenon calculated by the rule of a simple proportion in this month exceeds average monthly, length of radius will go beyond a circle and if the size appears less average monthly, then the termination of radius will be in a circle according to the increased scale.

Months are located clockwise and their terminations connect lines. So, e.g., the radial charts showing seasonal spread of acute gastrointestinal diseases (fig. 2) can look.

Plane charts represent statistical data in the form of plane geometrical figures. They can use for reflection of dynamics, structure of the phenomena, ratios various - processes.

Treat this type of charts stylar, intra stylar (intra tape), pyramidal and sector.

At creation of stylar charts on abscissa axis the equal bases of rectangles are postponed, and their height is defined by the level of the size of the phenomenon (process), according to the scale specified ordinate axes (fig. 3). Sometimes near the main phenomenon show also columns for other phenomenon connected with the basic.

Fig. 4. The intra stylar chart displaying structure of traumatism (by types of injuries) at various enterprises.

Intra stylar (intra tape) charts apply to the image of structure of the phenomenon in various collectives or in various spans. Height of all columns (or length of tapes) is equally equated to 100%. Each column (tape) is divided into pieces which correspond to a share (in %) a component of the phenomenon. Each structural part is conditionally designated in the form of this or that shading or color. The arrangement of ranks of such columns (or tapes) does foreseeable change of a share of each component and structure of the phenomenon in general (fig. 4).

Fig. 5. The pyramidal chart displaying age and sex structure of the population of the area N (conditional data); figures in the chart designate age.

Pyramidal charts intend for the image of age and sex structure of the population, comparison of prevalence of various diseases in the compared professions or territories (administrative, geographical, etc.). They represent modification of stylar charts in which the bases of columns are turned to each other, and rectangles are located parallel to abscissa axis, and on the one hand sizes of a sign for one contingent, and with another — for another are located. The reflected signs are specified in space between the bases of rectangles (forms of diseases or age groups; fig. 5).

Fig. 6. The sector chart displaying distribution of cases of traumatism for the reasons (in % to a result).
Fig. 7. The figured chart displaying growth of number of hospital beds in the city of N by years (one figure corresponds 10 000 beds, for example, an upper row — in 1950, lower — in 1970).

Sector charts are applied to the characteristic of structure of the phenomena. They represent the circle divided into the sectors corresponding to the specific weight of each of components of the reflected phenomenon. At transfer of percent of this part in degrees one percent is equal 3,6 °; each sector shall have the symbol — in the form of various shading (fig. 6) or color.

It is necessary to distinguish from sector D. circular in which the circle, without being divided into sectors, represents the sizes of the phenomenon in size of the radius. These D. are applied to the image of prevalence of the phenomena in these or those sets, but have no big visualization.

Dot charts are used by hl. obr. at pilot and laboratory studies when it is required to reflect the size of each separate observation and its quality standard on one or two combined signs. For this purpose against the background of stylar D. the points on number of the made observations indicating certain zones of combinations of the individual sizes of signs are put down.

Volume charts (a cube, a sphere, a pyramid) can be applied to reflection of the sizes of the phenomena, but in view of complexity of calculations and small visualization were not widely adopted.

Figured charts are used for reflection of prevalence of the phenomena in various spans or in various geographical zones. They represent statistical data in the form of figures and have big visualization. There are two options of figured. First option: one figure, but the different sizes — according to growth or decrease in the sizes of the phenomenon undertakes. However this option does not meet requirements of accuracy as it is difficult to reflect evenly in all proportions change of the sizes of a figure (a human body) or any subject. Therefore the second option, so-called scale figure is preferable: not the size of a figure, but their number (fig. 7) changes, each figure answers a certain scale. E.g., if it is required to represent growth of number of hospital beds, then the accepted standard figure (bed) is equated, e.g., to 10 thousand beds. Depending on that, in how many time the bed fund for the compared period increased, on figured D. it will be represented respectively number of figures: at 20 thousand beds — 2 figures (bed), at 30 thousand beds — 3 figures (bed) etc.


Bibliography: Kamensk L. S. Statistical processing of laboratory and clinical data, L., 1964; Kuvshinnikov P. A. A statistical method in clinical trials, page 14.8, M., 1955; Notkin E. L. Statistika in hygienic researches, page 50, M., 1965; Urlanis B. Ts. General theory of statistics, page 401, M., 1973.

E. L. Notkin.

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