graph presentation 2010

7/28/2019 Graph Presentation 2010

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Diagrammatic Representation of

Statistical Data&Classification of Graphs


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Diagrammatic Representation of

Statistical Data


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Diagrammatic Representation 1

Must be neat and workmanlike

i.e. pleasing to look at;

able to emphasize the important feature

i.e. choose a method which is possible todraw readers attention very quickly


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There are often 2 or more methods of

presenting the same statistics;

so choose the most informative, incisive and

effective one;

Do NOT put too much information on a

single map;


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Must include the KEY, TITLE, SCALE

or else:

MEANINGLESS !!!

Useful to do overlay i.e. based on the same base map


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The appreciation of a quantity represented

by a linear symbol is easier than represented

by an areal symbol

and it holds also to volume symbol;

Graphs for comparison ?

use the same scale !!!


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Basic equipment:

ruler (for refine marking);

pencil (HB, H/ 2H);

colour pencils;

compasses; dividers;

protractor & set rule (circle / square)


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Draw straight line by using a ruler,

i.e. no FREEHAND !!!

Using contrasting colour, esp. pie chart;

Avoid patches of tone grade;


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Sharp point of the pen should always be

maintained; SHARP !!!

Either printing or block capitals !

Horizontal !!!

CHECK your work !


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If you want to enlarge the scale ?

the graph must be clearly indicated of the

rate of exaggeration with note / explanation;

Cultivate the habit of examining statistical

maps whenever they appear;


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Make preliminary drawing;

Exercise your own creativity on making the

maps;

PRACTICE !PRACTICE! & PRACTICE !

because READING alone is not sufficient !


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Classificationof

Statistical Graphs


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Classification of Graphs:

1. Statistical Graphs;

2. Statistical Chart & Diagrams;

3. Statistical Maps.


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What are Statistical Graphs ?

They are graphs basically concerned with

the relationship between quantities and does

not stress the idea of location;

Drawn on the background of squared graph

paper;


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Statistical Graphs

1. Line & curve graphs

2. Bar graphs

3. Age and sex pyramids

4. Dispersion graphs

5. Semi-logarithmic graphs 6.Circular graphs


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Statistical Graphs- Line & Curve

Types of Line & Curve Graphs

a. simple

b. group or comparative

c. compound

d. divergence


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1a.Simple Line & Curve Graphs:I

CONSTRUCTION:

horizontal axis is normally used for

independentvariable; vertical axis fordependent variable;

the base of the vertical scale should be at

zero; the top should be slightly higher than the

maximum value to be recorded;


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1a.Simple Line & Curve Graphs:II

two different sets of values may be marked

on the two axes

e.g. oF and oC; hectares & acres

values marked on the vertical scale must not

stand on the horizontal lines but written so

that they would be bisected by thehorizontal line


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1a.Simple Line & Curve Graphs:III

Do not indicate large numbers with long

strings of noughts;

e.g. 100, 000 & 200, 000

but write, either at the top (preferably) or

along the side of the axis;

When plotting, do not use crosses or dots

surrounded by a circle to mark values.

Use just a dot - visible, not too prominent.


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1a.Simple Line & Curve Graphs: IV

GENERAL:

Very great care must be taken in choosing

both the vertical and horizontal scales;

Graphs used for the purpose of comparison

must be drawn on the same scale;


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1b. Group or Comparative Line I CONSTRUCTION:

Lines and curves should be clearly & easily

distinguishable from each other;

Different colours can be used or

different methods of drawing a line can be

employed. e.g.

--------, .., -.-.-.-. , ---.---.

The maximum number of lines or curves

on 1 statistical graph: 4 - 5 only.


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1b. Group or Comparative Line II

GENERAL:

sometimes advantageous to write essential

information on each line or curve ,

but dont exceed one or at the most two

words per line;

Crossing of lines or curves should beavoided as much as possible to reduce

confusion and the difficulty in interpretation.


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1c. Compound Line Graph: I

CONSTRUCTION:

Draw the largest item or the one that shows

the least fluctuation first;

Lines cannot cross each other;

Colouring or shading is of considerable help

in interpretation.


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1c. Compound Line Graph: II GENERAL:

As the base of any individual line graph is

not zero (except the bottom one); it must be

remembered that

only readings between the individual line

graphs can be considered;

Do not confuse the compound line graph

with the comparative (or group)line graph.

Difficult to find the value of individual item

though the total value is shown.


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1d. Divergence Line Graphs: I

CONSTRUCTION:

The Zero line is usually thickened;

Great care must be taken in choosing the

vertical scale;

The vertical scale can be in terms of values,

quantities or percentages.


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1d. Divergence Line Graphs: II

Values above average are calculated by

subtracting average from actual production

totals and plotted accordingly. The vertical axis must be scaled, both above

and below the zero line;

the upper part for positive, the lower fornegative values.


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1d. Divergence Line Graphs: II

GENERAL:

The graph does not normally show

production, exports, population and so on asabsolute totals;

It shows divergence, positive or negative,

from some particular or average;

It should not be used as a compound or

comparative line graph. (1 commodity only)


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2. Bar Graphs

a. Simple

b. Group (or Comparative)

c. Compound (or Divided)

d. Divergence


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2a. Simple Bar Graphs: I CONSTRUCTION: The horizontal scale: independent variable;

All bar must start at zero;

Bars may be drawn horizontally when the

time element is of minor significance;

e.g. production of 1 commodity by different

countries for a particular year

In such case, bars are usually arranged in

order of magnitude, the largest at the top.


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2a. Simple Bar Graphs: II

When vertical bars are drawn, the time

sequence is from left to right;

If there is missing item, space should be leftto indicate this.

The width of the bar is a matter of choice

but avoid bars that are too thick or too thin.


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2a. Simple Bar Graphs: III

GENERAL:

Bar graphs are often used in conjunction

with line or curve graphs;

e.g. climatic graph

e.g. hydrograph


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Group/Comparative Bar Graphs

Bars are grouped together for the purposes

of comparison;

The grouping of bars gives a betterimpression of totality and of the individual

contribution made by each of the

component parts; But does not give an accurate impression of

the total; Solution: bars drawn as % of the

total.


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2b. Group/Comparative Bar Graphs: I

CONSTRUCTION:

Basically the same as drawing simple bar

graphs;

Bars are usually drawn touching each other

to give an impression of totality;

Groups of bars must be separated from each

other;


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2b.Group/Comparative Bar Graphs: II

Use vertical group bars if the time element

is of considerable importance;

Draw the longest bar of the group on the left,proceeding in descending order to the right;

All bars must be of the same width and

drawn at right angles to the axis.

No writing need appear on the bars but a

key must be added.


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2b.Group/Comparative Bar Graphs: III

GENERAL:

Groups should be composed of not more

than 3 or 4 bars;

Bars may be drawn inside each other but

it is not recommended.


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2c.Compound/ Divided Bar Graphs ?

It is drawn by sub-dividing one bar into its

component parts.

The total length of the bar represents thetotal value of the component parts which are

shown as sub-division;


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2c.Compound/ Divided Bar Graphs I

CONSTRUCTION:

When draw vertically, the bars may be sub-

divided in descending order of size (thesmallest at the top);

Alternatively the component that shows the

least variation may be placed nearest thezero line;

Shading must indicate the same component.


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2c.Compound/ Divided Bar Graphs II

GENERAL:

Although the length of bars is easily and

quickly compared,

it is difficult to assess the value of any one

component or to trace its fluctuation over a

period of time.


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2d. Divergence Bar Graphs I

CONSTRUCTION:

The zero line must be clearly indicated;

usually by thickening;

The vertical axis must be scaled, both above

and below the zero line;

the upper part for positive, the lower for

negative values.


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2d. Divergence Bar Graphs II

Compound or group bars should not be used

to show divergence;

divergence bar graphs usually employ

simple bars only.


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3. OTHERS

Age & Sex Graphs / Pyramids

Dispersion Graphs

e.g. inter-quartile

Semi-Logarithmic Graphs

Circular Graphs


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Statistical Chart and Diagrams ?

Do not depend on squared graph paper nor

map;

Used in conjunction with a map for

defining or emphasizing location;

or drawn independently.


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Statistical Charts & Diagrams

1. Divided Circle (Pie Charts)

2. Divided Rectangle

3. Repeated Symbols

e.g. Proportional Circles

Proportional Squares

Proportional Cubes

Proportional Spheres

Wind Roses


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1. Divided Circle (Pie Charts) II

The largest component is usually placed to

the right of 12 oclock.

Small segments often present a problem andare best grouped together around 9

oclock;

To reduce errors to a minimum, anglesshould be measured on a cumulative basis;


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1. Divided Circle (Pie Charts) III

All printing on the pie chart should be in

block capitals and horizontal.

It is often advantageous to mark eitherabsolute or percentage values on the

relevant segment and to colour the segments

distinctively; Segments that are similar in character must

be grouped together;


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1. Divided Circle (Pie Charts) IV

Small segments should be coloured with a

bright colour or shaded by some distinctive

means; The number of segments will be dictated by

the nature of the statistics;

the greater the number of segments themore difficult the pie chart becomes to read;

7 - 8 segments would seem to be the max.


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1. Divided Circle (Pie Charts) V

GENERAL:

A striking and effective visual impression

can be given by a simple divided circle,especially if colours are used;

For comparison of the components ratherthan on comparison of totals -- 2 or moresimple divided circles of the samesize may be used.


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Statistical Maps ?

They stress the idea of

location and / or

spatial distribution;

based on a map as construction.


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Statistical Map ?

1. Dot Maps

2. Isoline Maps

3. Shading (Choropleth) Maps

4. Flow Maps


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THE END

Can you identify the different types of

graphs from our textbook?


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Other Graphic Techniques:

Scattered Graph: P.423, Fig. 16.5

Lorenz Curve: P.325, Fig. 13.8

Rank-size Rule: P.373, Fig. 14.23

P.374, Fig. 14.24

Nearest Neighbour Analysis P.371

Spearmans Rank Correlation Coefficient:

P.573

Location Quotient: P.518

graph presentation 2010

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