Sampling 1.4/1.8

Question 1

Sampling Population

Answer 1

A population is everything or everybody that is possibly involved in an investigation.

Question 2

What’s a Census

Answer 2

A survey or investigation on the whole population.

Question 3

Biased sample

Answer 3

A sample which is not representative of the whole population.

Question 4

Stratified Sampling

Answer 4

Selects a random sample from each stratum of the population in proportion to the size of that stratum.

Question 5

Sampling Units

Answer 5

People or items that are to be sampled.

Question 6

Sampling Frame

Answer 6

A list of the people or items that are to be sampled.

Question 7

Formula for the PCRM (Peterson Capture-Recapture Method)

Answer 7

m/n = M/N

Question 8

Random Sample

Answer 8

Every member of the population has an equal chance of being included.

Question 9

How often is the U.K National Census conducted?

Answer 9

Every 10 years.

Question 10

Sample

Answer 10

A segment of the population that is representative of the population.

Question 11

Advantages of a Census?

Answer 11

• Unbiased
• Accurate
• Accounts for the whole pop.

Question 12

Advantages of a Sample?

Answer 12

• Cheap
• Less time consuming
• Less data to be considered.

Question 13

Dis-advantages of a Census?

Answer 13

• Time-consuming
• Expensive
• Hard to make whole population respond
• Hard to involve whole population
• Lots of data to be handled.

Question 14

Dis-advantages of a Sample?

Answer 14

• Not fully representative

- May be biased

Question 15

Why is a larger sample more representative?

Answer 15

Anomalous results could skew small data sets to look even. More people = more accuracy.

Question 16

What (4) assumptions are made with the Peterson capture re-capture method?

Answer 16

• Population stays the same (no births & no deaths or no leaving the habitat)
• The probability of capture is the same for each individual
• The marks (tags) will not be lost and are always recognisable
• The sample size is large enough to be representative of the population.

Question 17

Advantages of random sampling?

Answer 17

• Sample is more likely to be representative of the population, provided it is large.
• Probability of being chosen is the same fro each member of the population.

Question 18

Disadvantages of random sampling?

Answer 18

• Needs a full list of the whole population

- Needs a large sample size.

Question 19

List 5 non-random sampling methods:

Answer 19

• Judgement
• Opportunity
• Cluster
• Systematic
• Quota

Question 20

Judgement Sampling

Answer 20

Using a judgement to select a sample that is representative of the population.

Question 21

Opportunity Sampling

Answer 21

Using the people (or objects) that are available at the time.

Question 22

Cluster Sampling

Answer 22

Randomly selecting clusters (natural groups) to make a sample.

Question 23

How do you perform Systematic Sampling?

Answer 23

Choose a starting point within the frame at random, and then choose every item at a regularly occurring interval.

Question 24

Quota Sampling

Answer 24

A (quota) number of people are chosen to be assessed from each group.

Question 25

When is Cluster Sampling used?

Answer 25

When the data naturally splits into groups

Question 26

When is Quota Sampling used?

Answer 26

When the population is grouped into characteristics such as age/gender.

Question 27

What should be considered when choosing a sample?

Answer 27

- Whether it is biased - Whether sample size is suitable - How quick and easy the method is - How expensive it is to carry out.

Question 28

Stratified sample

Answer 28

Contains members of each stratum in proportion to the size of that stratum. The sample from each stratum is selected randomly.