Sampling and data

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Sampling techniques for primary data collection

Shortcut method for investigating the whole population as there is not enough time to, equipment and labour to measure every single item so the sample must be representable and statically valid to the whole population.

1) the larger the sample the more accurate it is at representing the population

2) A sample with the least bias is the most statistically vaild

3) sample size needs to be balanced between obtaining a statistically valid representation, time, labour and equipment available. 

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Random sampling

  • The least bias as there is no subjectivity
  • Each member of the population have equal chance of being picked 
  • Can be obtained by random number generator

ADVANTAGES

  • Can be used with large sample populations
  • Avoids the unavoidable bias of personally choosing a sample 

DISADVANTAGES

  • Can lead to poor representation 
  • The people chosen may not give consent to be in the study and therefore the sample becomes biased with only the ones willing being left. 
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Systematic sampling

  • Evenly/ regularly distributed in a spatial context 
  • They can be at equal/ regular intervals in temporarl context
  • They can be regularly numbered

ADVANTAGES

  • More straight forward to random sampling
  • Good coverage of whole sample area

DISADVANTAGE

  • More biasnas not all members have an equal chance of being selected
  • An over or under representation of the population may be created
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Stratified sampling

This method is used when the parent population is made up of sub-sets of known size. These sub-sets make up different proportion of the total population and therefore the sampling needs to be stratefied to ensure the results are proportional and respresentive as a whole. 

ADVANTAGE

  • Can be used with random or systematic sampling, point or line techniques.
  • If proportions of the sub-units are known is can generate results which are more representative of the whole population
  • It is very flexible and used in many geographical enquiries
  • Correlations and comparisons can be made between the subsets

DISADVANTAGES

  • The proportions of the subunit must be known and accurate if to be worked out properly
  • Hard to stratify questionnaire data collection
  • Accurate up-to-date population data must be known and it may be hard to identify peoples age or social background effectively
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Using secondary data

Data which already exsists. Sources include libraries, annual reports, Census reports, governmental data, 

AVANTAGES

  • Economical- saves time and effort of carrying out own research
  • Improves overall data collection as it may have data that you yourself cannot collect due to resources, location etc
  • Use it to work out what the gaps are and extra needs in our own data
  • Helps improve out understanding of the investigation
  • Provides comparison for the data collected by the researcher

DISADVANTAGES

  • Acuracy of data may be unknown
  • Data may be outdated
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Remote sensed data (satellite imagery)

Can be used for weather forecasting and predicting natural hazards (storms, volcanic eruptions- bulges in a volcano, earthquakes- movement of tectonic plates)

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Data bases (census date)

Able to access huge anount of data that has ben collected over a whole city, region, country and compare with other data sets taken from different places or same data set taken at different times. 

Good way of storing a lot of data and recording the growth of cities etc 

Can be used by companies and governments when makking policies 

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GIS data

Cartographic modelling of land use, soil vegetation, land ownership, characterists.

ADVANTAGES

  • Bypass the mechanical proccesses of maping
  • Higher quality
  • can be acessed anywhere with internet

DISADVANTAGES

  • Expensive- cant be used all round the world
  • Needs regular updating
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Use of IT

Uses them for databases, graphical and cartographic images

ADVANTAGES

  • Easy to make comparisons over time
  • Saves time
  • Can be converted into graphs for visual representation
  • Easy and quicker to use if the data set is large

DISADVANTAGES

  • Can be expensive
  • Need computers and internet
  • Not available everwhere
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Comments

ava.scott

this is soo interesting, and enlightening. are you jesus?????

8cburton

in my free time yeah, but unable to get out recently, thats why the world has been lacking in some miricals, but il be back at it after exams

ava.scott

Omg can u make my exams be A's!???? 

8cburton

sure il just go ask God to dish me out some magic credits

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