STATISTICAL METHODS

COMPOUND/CUMULATIVE BAR GRAPH

Construction
Example

When constructing a compound bar graph ,the following steps are followed

Major cash crops exported in Kenya in tonnes

CROP 1990 1991 1992 1993 1994

COFFEE 4500 5000 5200 6000 5900

TEA 1300 1100 2500 2100 2200

MAIZE 800 900 500 400 400

WHEAT 600 500 600 700 500


 1.Set the totals for the data for each year

CROP 1990 CT 1991 CT 1992 CT 1993 CT 1994 CT
COFFEE 4500 4500 5000 5000 5200 5200 6000 6000 5900 5900
TEA 1300 5800 1100 6100 2500 7700 2100 8100 2200 8100
MAIZE 800 6600 900 7000 500 8200 400 8500 400 8500
WHEAT 600 7200 500 7500 600 8800 700 9200 500 9000
TOTAL 7200 7500 8800 9200 9000

2.Draw vertical axis(Y) to represent dependent variable
3.Draw horizontal axis(x) to represent independent variable
4.Label both axis using suitable scale
5.Plot the cumulative values for each year
6.Use values for components to subdivide the cumulative bar
7.The subdivisions are placed in descending order with the longest at the bottom(coffee)
8.Shade each component differently
9.Put title and key

Advantages

  1. Its easy to construct
  2. It has good visual impression
  3. There is easy comparison for the same component in different bars because of uniform shading
  4. Easy to interpret because bars are shaded differently

Disadvantages

  1. It doesn‟t show the trend of components (change over time).
  2. Cant be used to show many components as there is limited space upwards
  3. Tedious as there is a lot of calculation work involved.
  4. Not easy to trace individual contribution made by members of the same bar
  5. Poor choice of vertical scale causes exaggeration of bars length leading to wrong conclusions












PIECHART/DIVIDEDCIRCLES/CIRCLE CHARTS

A circle which has been subdivided into degrees used to represent statistical data where component values have been converted in degrees.

Major countries producing commercial vehicles in the world in 000s

USA FRANCE JAPAN UK GERMANY RUSSIA
1800 240 2050 400 240 750

Steps

  1. a) Convert components into degrees

USA 1800×360/5480=118.2◦
FRANCE 240×360/5480=15.8◦
JAPAN 2050×360/5480=134.7◦

UK 400×360/5480=26.3◦

  • 2.Draw a circle of convenient size using a pair of compasses.
  • 3. From the centre of the circle mark out each calculated angle using a protractor.
  • 4. Shade the sectors differently and provide the key for various shadings.


Advantages

  1. Gives a good/clear visual impression
  2. Easy to draw.
  3. Can be used to present varying types of data e.g. minerals, population, etc.
  4. Easy to read and interpret as segments are arranged in descending order and are also well shaded.
  5. Easy to compare individual segments.

Disadvantages

  1. Difficult to interpret if segments are many
  2. Tedious due to a lot of mathematical calculations and marking out of angles involved.
  3. Can‟t be used to show trend/change over a certain period.
  4. Small quantities or decimals may not be easily represented.

Analysis

  1. The main producer of commercial vehicles is Japan.
  2. The second largest producer is USA followed by Russia.
  3. The lowest producers were France and West Germany with.









PROPORTIONAL CIRCLES

This is use of circles of various sizes to represent different sets of statistical data.

Table showing mineral production In Kenya from year1998-2000

MINERALS QUANTITY IN TONNES

1998 1999 2000

Graphite 200 490 930

Fluorspar 30 255 450

Soda ash 270 300 350

Diamond 500 870 1270

TOTAL 1000 1915 3000

Steps

  1. Determining the radii of circles by finding the square roots of the totals

1998 √1000=31.62=32

1999 √1915=43.76=44

2000 √3000=54.77=55
2.Scale:1cm represents 10 tonnes

1998=3.2 cm

1999=4.4 cm

2000=5.5 cm
3.Using a pair of compasses draw circles of different radii representing mineral production in Kenya

between 1998 and 2000.

4.Convert component values into degrees

Component value/ total value of data×360
1998: Graphite-200/1000×360=72◦
Fluorspar-30/1000×360=10.8◦
Soda ash-270/1000×360=97.2◦

5.Diamond-500/1000×360=180◦
1999: Graphite-490/1915×360=92.1◦
Fluorspar-255/1915×360=47.9◦
`300/1915×360=56.4◦

Diamond-870/1915×360=163.6◦
2000: Graphite-930/3000×360=11.6◦
Fluorspar-450/3000×360=54◦
Soda ash-350/3000×360=42.1◦
Diamond-1270/3000×360=152.3◦

  1. On the proportional circle for each year use a protractor and mark out the angles
  2. Shade the segments and then provide a key.

Advantages

  1. They give a good visual impression.
  2. Easy to compare various components.
  3. Simple to construct.
  4. Easy to interpret as segments are arranged in descending order.
  5. Can be used to present varying types of data.

Disadvantages

  1. Tedious in calculation and measurement of angles
  2. Actual values represented by each component cant be known at a glance
  3. Difficult to accurately measure and draw sectors whose values are too small.
  4. Comparison can be difficult if the circles represent values which are almost equal.

Analysis/Conclusions

  1. Diamond was leading in production.
  2. The second leading mineral in production was graphite.
  3. The mineral with the lowest production was fluorspar.



Peda.net käyttää vain välttämättömiä evästeitä istunnon ylläpitämiseen ja anonyymiin tekniseen tilastointiin. Peda.net ei koskaan käytä evästeitä markkinointiin tai kerää yksilöityjä tilastoja. Lisää tietoa evästeistä