STATISTICS

STATISTICS

STATISTICS

GRAPHS

2 dimensional drawings which show relationships between 2 types of data representing two items also called variables. These are dependent variable which is affected by the other e.g. temperature (on y axis) and independent variable whose change is not affected by the other e.g. altitude (on x axis).

Steps

  • Draw x and y axis.
  • Choose suitable scale to accommodate the highest and lowest value.
  • Plot the values accurately using faint dots.
  • Join the dots using curved line. If it’s a bar graph the dots should be at the middle of the top line. Years should also be at the middle. You should have also decided on the width of the bars.
  • In data without continuity e.g. crop production there should be gaps between bars and for one with continuity e.g. rainfall bars should not have gaps.
  • Draw vertical lines on either side of the dot then draw horizontal line to join them with the dot.
  • Shade uniformly if they are representing only one type of data and differently if representing one type of data.
  • In combined line and bar graph temperature figures are plotted on the right hand side of y-axis while rainfall on the left
  • Don’t start exactly at zero.
  • Include temperature and rainfall scales.
  • Start where the longest bar ends.

What a Well Drawn Graph Should Have

  • Title
  • Scale/scales
  • Labelled and marked x and y axis starting at zero.
  • Key if required e.g. in comparative bar graph.
  • Accurately plotted and lines, curves or bars properly drawn.

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Simple Line graph

Advantages

  • Easy to construct
  • Easy to interpret
  • Easy to read/estimate exact values.
  • Shows trend or movement overtime.

Disadvantages

  • Doesn’t give a clear impression on the quantity of data.
  • May give false impression on the quantity especially when there was no production.
  • Poor choice of vertical scale may exaggerate fluctuations in values.
  • Difficult to find exact values by interpolation.

Simple Bar Graph/histogram

Advantages

  • Easy to construct.
  • Easy to interpret.
  • Easy to read.
  • Gives a clear visual impression on the quantity of data.

Disadvantages

  • Poor choice of vertical scale may cause exaggeration of bars.
  • Doesn’t show continuity/ variation of data overtime.
  • Unsuitable technique when values exist in continuity.
  • Not possible to obtain intermediate values from the graph.

Combined Line and bar Graph

Advantages

Easy to construct.

Easy to read.

It shows relationship between two sets of data.

Disadvantages

  • Difficult to choose suitable scale when values of variables differ by great magnitude.
  • Considerable variation of data represented by the line may cause the line the bars thus obscuring the relationship.
  • Doesn’t show relationship between the same sets of data of more than one place.

Temperature and Rainfall for Thika

Month J F M A M J J A S O N D
Temp(◦c) 24 24 23 22 19 17 17 18 19 20 22 23
Rainfall(mm) 109 122 130 76 52 34 28 38 70 108 121 120

Analysis and Interpretation

  • The month with heaviest rainfall is May.
  • The month with lowest rainfall is July.
  • The hottest month was January and February.
  • The months with lowest temperature were June and July.

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Crop Production in Kenya in the Years 2001 and 2002

 

crop Amount in metric tonnes
  2001 2002
Tea 300,000 500,000
Coffee 120,000 80,000
wheat 120,000 150,000
Maize 250,000 400,000

STATISTICS II

Value of export Crops from Kenya (ksh million)

Crop 1997 1998 1999 2000 2001
Tea 24126 32971 33065 35150 34485
Coffee 16856 12817 12029 11707 7460
Horticulture 13752 14938 17641 21216 19846

If the data has large figures e.g. 195262 plot in 1000s=195, 184,988=185.

You can draw comparative/group/multiple line and bar graphs from the data.

Comparative/Group/Multiple Line Graph

Advantages

  • Simple to construct
  • Suitable when comparing trends or movements
  • Comparison of items is easy because the graphs are drawn using common axis
  • Its easy to read exact values from each graph

Disadvantages

  • Number of items which can be represented are limited
  • Crossing of lines may make interpretation and comparison difficult and confusing.
  • Total amount of variable cant be established at a glance.

Comparative Bar Graph

Advantages

  • Easy to construct
  • Easy to read and interpret
  • Easy to compare similar components within different bars.
  • Gives a good impression of totality.
  • Individual contribution made by each component is clearly seen.
  • Differences in quantity of components are clearly seen.

Disadvantages

  • Doesn’t show trend of components over time.
  • Not easy to compare components where bars are many
  • Not suitable for many components.

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Divided Bars or Rectangles

Production of Sugarcane in 1000 tonnes of 5 major factories in Kenya

Factory Production(ooo tonnes) Length in cm
Sony 50 0.5
Nzoia 100 1
Chemilil 200 2
Muhoroni 250 2.5
Mumias 400 4
Total 1000 10

Reported Visitor Arrivals by Continent for the Year 2000

Continent No. of visitors Length of strip (cm)
Africa 153904 1.5
America 77271 0.8
Asia 58784 0.6
Europe 663906 6.6
Other 82672 0.8
Total   10.3

STATISTICS II

Look for a convenient scale say 1cm rep 100000 visitors

  • Draw a divided rectangle 10 cm long to represent the data.
  • Show your calculations.

-It should have the following:

  • Title
  • Different shades
  • Key
  • Width of 2cm

Analysis and Interpretation

To get the meaning of

  • Factory leading in sugar production is Mumias.
  • The 2nd leading is Muhoroni.
  • Factory with the lowest production of sugar is Sony.
  • Calculation of %s.

Advantages

  • Easy to construct
  • Easy to compare components because they are arranged in ascending or descending order.
  • Takes less space than when the data is presented using graphs.
  • Each component proportion to the total can easily be seen at a glance.

Disadvantages

  • Can’t be used for a large data.
  • Only one unit of measurement can be used.
  • Difficult to asses values of individual component
  • The visual impression isn’t as good as pie charts.

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STATISTICS II

Exercise

Temperature and Rainfall for Kisumu

Month J F M A M J J A S O N D
Temp(◦c) 19 20 20 18 20 19 19 18 18 18 18 18
Rainfall(mm) 18 38 66 127 114 84 112 104 69 56 38 31
  • Draw a bar graph to represent rainfall figures.
  • Calculate the mean monthly temperature for the place.
  • Calculate the mean annual temperature range.
  • calculate the annual rainfall totals.

2.

Temp/Day Mon Tue Wed Thurs Fri Sat Sun
Max ◦c 28 27 28 26 29 29 26
Min ◦c 18 18 20 16 22 21 19
  • Calculate the diurnal/daily temperature range for Tuesday.
  • Calculate the mean daily temperature for Sunday.
    1. Suppose at 40 ◦c air can hold 60g/m3 of water vapour and the maximum vapour it can hold is 70g/m3. Calculate the relative humidity.
    2. (a) Calculate the time at Lamu 70◦E when time at GWM is noon.

(b) Calculate the longitude of Watamu whose time is 6pm when time at GWM is 9am.

  1. Students from a certain school obtained the following marks in their end of term geography examination.

74, 52, 48, 60, 48, 32, 80, 67 and 85.

Calculate the following:

  • Median
  • Mode
  • Mean
  • State their advantages and disadvantages.
    1. (a) Calculate the scale given that the ground distance is 200km while the distance on the map is 20cm.

(b) A student measured the length of a road on a map from point A to B and found it to be 3.6 cm. Use a scale of 1:50000 calculate the actual/ground distance in km.

  1. Students intend to carry out field study of a forest around their school.
  • State two ways in which they’d prepare themselves.
  • State 2 objectives they’d have formulated for their study.
  • List two problems they’d have encountered in the field.
  • State two follow up activities they would have after the field study.

 

ALL GEOGRAPHY NOTES FORM 1-4 WITH TOPICAL QUESTIONS & ANSWERS

PRIMARY NOTES, SCHEMES OF WORK AND EXAMINATIONS

 

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