Stage 2

Question 1

Define sampling

Answer 1

A subset of items taken from the whole population (all the data available).

Question 2

When is sampling used?

Answer 2

It is used when:
•The population is too large to study each individual
•Time is limited
•Collecting data is destructive and you are trying to minimise damage

Question 3

What are the 4 features of a good sample?

Answer 3

1. Unbiased
2. Precise
3. Appropriate size
4. Easily collected

Question 4

Features of a good sample:

unbiased

Answer 4

A sample where the mean and standard deviation of the sample is neither larger or smaller than the values for the whole population

Question 5

Features of a good sample:

precise

Answer 5

A sample that provides an accurate estimate of the population characteristics. It does not distort patterns/trends and does not exaggerate anomalies

Question 6

Features of a good sample:

Appropriate size

Answer 6

A sample that is large enough to produce conclusive results in terms of statistical significance (a sample size of over 12 is considered large enough for making reliable conclusions using statistical testing e.g. Spearman’s Rank), but small enough to be done well.

Question 7

Features of a good sample:

Easily collected

Answer 7

Can be easily collected within the time/ equipment and researchers available

Question 8

What should a plan of a geographical investigation include?

Answer 8

1. Sampling frame
2. Sampling number
3. Sampling Design
4. Plan of timing/sampling/ division of labour

Question 9

Components of a plan of a geographical investigation;

Sampling frame

Answer 9

Sampling frame which clearly defines the outline of the area you will be investigating and a justification for choosing this area

Question 10

Components of a plan of a geographical investigation;

Sampling number

Answer 10

Sampling number which is sufficient to provide a reliable sample but practical for collecting within the time scale and with the number of researchers available

Question 11

Components of a plan of a geographical investigation;

Sampling design

Answer 11

Sampling design which clearly describes and justifies the choice of sampling technique employed.

• Sampling type could be grid, point or transect
• Sampling strategy could be random, systematic, stratified or pragmatic
• It is advisable to draw a sketch of the area to show the locations of the sampling sites

Question 12

Define: sampling frame

Answer 12

The study area or group from which the sample is selected (e.g. area on an OS map, electoral register, telephone directory, every person entering a shopping centre)

Question 13

Define: target population

Answer 13

Total set of measurements relevant to a study (e.g. all possible measurements of pebble size from a beach which are useful for the investigation)

Question 14

Define: sampled population

Answer 14

Measurements for the area which is accessible to the investigation (e.g. pebbles which are exposed on the surface of the beach)

Question 15

Define: sample size

Answer 15

The number of measurements in a sample. For further statistical analysis this is usually a minimum of 30

Question 16

Define: population parameter

Answer 16

A true summary measurement of the characteristics of the target population (e.g. mean size of pebbles on a beach). If the parameter is based on a sample, it is only an estimate

Question 17

Define: bias

Answer 17

This occurs when the sample measurement over- or under-estimates the population parameter. May be introduced unconsciously (e.g. including certain places because they are more accessible or interviewing a certain age group/gender of shoppers because of the time of day/day of the week)

Question 18

Define: sampling error

Answer 18

The difference between a sample estimate and the population parameter

Question 19

Define: representative sample

Answer 19

A sample that minimised bias

Question 20

What are the three main types of spatial sampling?

Answer 20

1. Point sampling
2. Line sampling
3. Area sampling

Question 21

spatial sampling - What is point sampling?

Answer 21

a selection of specific points within an area

Question 22

spatial sampling - What is line sampling?

Answer 22

sampling along a line through (e.g.) a city or across a sand dune

Question 23

spatial sampling - what is area sampling?

Answer 23

when an area is sub-divided into a selection of sample squares

Question 24

Sampling Type : Random

What is the method for random sampling?

Answer 24

Use number tables to generate random coordinates

Question 25

Sampling Type : Random What are the advantages of random sampling?

Answer 25

1. Least biased because every individual has equal chance of being selected 2. Relatively quick and easy to select sample types

Question 26

Sampling Type : Random What are the disadvantages of random sampling?

Answer 26

1. May not take samples from a whole survey area 2. Important variations may not be sampled and therefore you may not obtain a truly reliable sample 3. Theoretically the same individual could be selected more than once

Question 27

Sampling Type : Systematic What is the method for systematic sampling?

Answer 27

Samples are regularly spaced e.g. every 100m along a transect

Question 28

Sampling Type : Systematic What are the advantages of systematic sampling?

Answer 28

1. Quick and easy method 2. Samples taken from all parts of the survey area so the whole area is covered 3. No individual is selected more than once

Question 29

Sampling Type : Systematic What are the disadvantages of systematic sampling?

Answer 29

1. The regular interval may miss an important variation e.g. the top of the dune or a dune slack 2. You may sample and evenly spaced characteristic which means the sample is unreliable because it over emphasises the importance of the regular feature

Question 30

Sampling Type : Stratified What is the method for stratified sampling?

Answer 30

- sampling frame divided into sub-sets - number of samples is taken from each subset in proportion to it's relative importance (e. g. sand dunes is taken at a change of slope.)

Question 31

Sampling Type : Stratified What are the advantages of stratified sampling?

Answer 31

1. Can provide greater precision than a random sample | 2. It requires greater precision, so often requires a smaller sample than for random sampling. This saves money.

Question 32

Sampling Type : Stratified What are the disadvantages of stratified sampling?

Answer 32

1. May be difficult to get background data to allow for reliable sampling 2. Can introduce bias because researcher selects predetermined factors as being important e.g. land use or age/gender of population

Question 33

Sampling Type : Pragmatic What is the method for pragmatic sampling?

Answer 33

Samples are only taken from areas which is safe or accessible

Question 34

Sampling Type : Pragmatic What are the advantages of pragmatic sampling?

Answer 34

1. Quick, easy and SAFE

Question 35

Sampling Type : Pragmatic What are the disadvantages of pragmatic sampling?

Answer 35

1. Will not take samples from the whole survey area so important variations may not be sampled 2. May not obtain a truly reliable sample 3. Bias is introduced

Question 36

What is a risk assessment?

Answer 36

identification and evaluation of the risks involved in undertaking research and the strategies that can be taken to minimise these risks

Question 37

What is a physical risk?

Answer 37

risks of harm or injury to the researchers caused by the environment

Question 38

What is a statistical risk?

Answer 38

A risk that the data collected does not accurately represent the whole population because of bias in the sampling technique or errors in data collection.

Question 39

When are statistical risks introduced into an investigation?

Answer 39

Statistical risk is introduced into an investigation when: 1. Insufficient samples are taken or the sampling technique is not well planned so that not all the population is represented in the same sample 2. Data collection methods can cause risk when the equipment is inaccurate or the researchers lack precision

Question 40

Name 5 methods for reducing statistical risks :

Answer 40

1. Sufficient samples need to be taken and the samples must cover as much of the sample frame as possible 2. The sample size must be large enough for statistical testing to be used with confidence. A sample size of at least 12 is needed 3. A careful balance between the number of samples needed and the time/researchers available must be made 4. Highly accurate equipment must be used 5. Researchers must be trained so that they can use the equipment accurately

Question 41

Pilot Survey What is a pilot survey?

Answer 41

A prior visit to the investigation site or practising your questionnaires with friends/family prior to the real investigation

Question 42

Pilot Survey What are the advantages of a pilot survey?

Answer 42

1. To assess the accessibility of the site 2. To assess the physical risks of the site 3. To practise data collection methods to ensure more accuracy 4. To make sure that the sampling techniques and data collection methods selected will result in the required data being collected for the investigation 5. To help refine data collection sheets 6. To identify any unforeseen risks both physical and statistical

Question 43

Pilot Survey What are the disadvantages of a pilot survey?

Answer 43

1. Time consuming 2. Costly 3. Might be hard to access location