Statistics - Geography Form 3 Notes

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Compound/Cumulative/Divided Bar Graph

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

Steps

CROP

1990

CT

1991

CT

1992

CT

1993

CT

1994

COFFEE

4500

4500

5000

5000

5200

5200

6000

6000

5900

TEA

1300

5800

1100

6100

2500

7700

2100

8100

2200

MAIZE

800

6600

900

7000

500

8200

400

8500

400

WHEAT

600

7200

500

7500

600

8800

700

9200

500

TOTAL

7200

7500

8800

9200

9000

  1. Set cumulative totals for the data each year
  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. It’s 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
  5. Total value of the bar can be identified easily

Disadvantages

  1. It doesn’t show the trend of components (change over time).
  2. Can’t 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

Divided Bar Graph

Analysis

  • Coffee was the leading export earner in the five years.
  • Tea was the second leading export earner.
  • Wheat had the lowest export quantity.
  • 1993 recorded the highest export quantity.
  • 1990 recorded the lowest export quantity.


Piechart/Divided Circles/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. Convert components into degrees
    USA 1800/5480×360=118.2◦
    FRANCE 240/5480×360=15.8◦
    JAPAN 2050/5480×360=134.7◦
    UK 400/5480×360=26.3◦
    GERMANY 240/5480×360=15.8◦
    RUSSIA 750/5480×360=49.3◦
  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.

pie chart.PNG



Proportional Circles

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

Table showing mineral production In Kenya from year 1998-2000

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
  1. Scale:1cm represents 10 tonnes
    1998=3.2 cm
    1999=4.4 cm
    2000=5.5 cm
  1. Using a pair of compasses draw circles of different radii representing mineral production in Kenya between 1998 and 2000.
  2. 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◦
    Diamond-500/1000×360=180◦

    1999: Graphite-490/1915×360=92.1◦
    Fluorspar-255/1915×360=47.9◦
    Soda ash`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.

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Read 9098 times Last modified on Monday, 17 January 2022 10:01
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