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Maths > Sampling > Flashcards

Sampling Flashcards

1
Q

Population

A

The whole set of items that are of interest

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2
Q

Sample

A

Some subset of the population that represents the population

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3
Q

Census

A

Data collected from the entire population

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4
Q

Sampling frame

A

List of the samples

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5
Q

What are the advantages of a census?

A
  • Completely accurate
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6
Q

What are the disadvantages of a census?

A
  • Large volume of data to process
  • Time-consuming
  • Expensive
  • Testing may lead to destruction
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7
Q

What are the advantages of sampling?

A
  • Cheaper
  • Quicker
  • Less data to process
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8
Q

What are the disadvantages of sampling?

A
  • May not be large enough to represent small strata
  • May be inaccurate
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9
Q

Method of simple random sampling:

A
  • Assign each item an identifying number
  • Use a bias-free method like RNG to generate numbers
  • Use these identifying numbers to select the items
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10
Q

What are the advantages of simple random sampling?

A
  • No bias
  • Cheap
  • Easy
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11
Q

What are the disadvantages of simple random sampling?

A
  • Not suitable for a large population
  • Sampling frame is needed
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12
Q

Method of systematic sampling:

A
  • Assign each item an identifying number
  • Calculate the sampling interval by dividing the population size by the sample size you want eg. 500/100 = 5
  • Choose a random starting point eg. 42
  • Sample each item with an interval from the starting point eg. 47, 52, 57 and so on
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13
Q

What are the advantages of systematic sampling?

A
  • Suitable for large population
  • Quick
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14
Q

What are the disadvantages of systematic sampling?

A
  • Sampling frame is needed otherwise it’s biased
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15
Q

Method of stratified sampling:

A
  • Divide the sample size you want (1 strata) by the whole population size
  • Multiply this by the other strata’s to identify how many people you need of each
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16
Q

What are the advantages of stratified sampling?

A
  • Reflects population structure
  • Guarantees proportional representation
17
Q

What are the disadvantages of stratified sampling?

A
  • Pop needs to be clearly divided eg. year groups in a school
18
Q

Method of quota sampling:

A
  • Determine your quota eg. 20 ppl from US, 20 ppl from UK
  • Select people to fit into stratas of specific characteristics eg. Born in the UK, born in US
  • Continue selecting until the quota is met
19
Q

What are the advantages of quota sampling?

A
  • A small sample can still be represented
  • Sampling frame is not needed
  • Quick
  • Provides an easy comparison
20
Q

What are the disadvantages of quota sampling?

A
  • Biased
  • Possible inaccurate division of strata
  • Time-consuming
  • Non-responses are not recorded
21
Q

Method of self-selected sampling:

A

Samples are selected by the researcher

22
Q

What are the advantages of self-selected sampling?

A
  • Quick
  • Easy
23
Q

What are the disadvantages of cluster sampling?

A
  • Unlikely to provide a representative sample
24
Q

Method of opportunity sampling:

A
  • Sample people that are available at the time of your study eg. First 20 people you see
25
Q

What are the advantages of opportunity sampling?

A
  • Easy
  • Cheap
26
Q

What are the disadvantages of opportunity sampling?

A
  • Highly dependent on individual researcher
  • Not representative
27
Q

Method of cluster sampling:

A
  • Define each cluster eg. 10 random stores (clusters) where Argos employees work
  • Collect sample from each cluster eg. Survey all those employees
28
Q

What are the advantages of cluster sampling?

A
  • No sampling frame
  • Cheap
29
Q

What are the disadvantages of self-selected sampling?

A
  • Likely to be biased
30
Q

What sampling methods should be used if you have a sampling frame?

A
  • Simple random
  • Stratified
31
Q

What sampling methods should be used if you do not have a sampling frame?

A
  • Quota
  • Opportunity
  • Cluster
  • Self-selected
32
Q

Sampling unit

A

One member of a sample

33
Q

Which method does not need a sampling frame, but may be biased if one is not present?

A

Systematic sampling

34
Q

Outlier

A

A data item that does not follow the pattern

35
Q

Formula for an outlier lower than the trend:

A

Q1 - k(Q3 - Q1)

36
Q

Formula for an outlier higher than the trend:

A

Q3 + k(Q3 - Q1)

37
Q

What is Q1, Q2 and Q3?

A

Q1 - Lower quartile
Q2 - Median
Q3 - Upper quartile

Maths (1 decks)

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