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Lorretta Salkeld 13P


Unit 4 geographical skills
Sampling methods- Systematic sampling
Used when studying areas including environmental gradients
Sample points should be evenly spaced or distributed
It is quick and easy but it is easy to miss variations
Types of systematic sampling
o Point sampling
o Line sampling
o Area…

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Lorretta Salkeld 13P

Avoids bias
Disadvantages:
Can lead to poor representation of population or area if large areas are not hit by random
sampling, distorting results
Practical constraints- time available and access to certain parts of the study area

Stratified sampling
Is used when the population or sampling frame is…

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Lorretta Salkeld 13P

Line graphs
Simple line graph- shows single series of data
Comparative line graph- shows two or more on the same graph and use the same scales
Divergent line graph
Strengths:
Easy to draw and understand
Can show both positive and negative values
Displays relative numbers and proportions…

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Lorretta Salkeld 13P

Circle size can also be made proportional to total quantity to compare different
populations
Summarises large data
Easily understood due to widespread use

Weaknesses:
May not show numerical data
Can get crowded with too many divisions
Categorical data only
Won't know exact values
Easily manipulated
Fails to…

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Lorretta Salkeld 13P

Can show previously unseen patterns e.g. log graphs show increase in world population to
be slowing down, normal graphs do not show this slow down.

Weaknesses:
Cannot start from 0
May make some relationships appear different as parabolic curves on a normal graph
become straight on log…

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Lorretta Salkeld 13P

Measured over a set period of time
Strengths:

Strong visual impression of both volume of movement & direction

Weaknesses:

Parts of the map may be obscured/crowded and difficult to interpret
Not appropriate for lots of variables

Desire line
Shows the strength of people who move from point…

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Lorretta Salkeld 13P

One variable only
Inexact ­ not the actual data

Isoline map
Maps showing lines drawn through points of equal value
Often used with colour between isolines to more clearly depict trends

Strengths:

Show more gradual change than choropleths ­ avoid abrupt change
Can clearly see boundaries
Show…

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Lorretta Salkeld 13P

Testing for a relationship between two variables
If number is above critical value must accept the alternative hypothesis- there is a
relationship
If number is below the critical value, accept the null hypothesis- there is no relationship
Formulate a null hypothesis individually rank values of each variable…

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Lorretta Salkeld 13P

Weaknesses:
Can't be used if there are less than five sets of data
Uses ranking so loses raw data

Chi Squared
Process:

Null hypothesis ­ `no relationship between distribution of... and of...'
Subtract observed frequencies from expected
Square result
Divide this by the expected value for that…

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Lorretta Salkeld 13P




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