Populations and samples Flashcards

1
Q

Population & sampling unit

A

Population - whole set of items of interest
SU - individual units of a population

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2
Q

Census

A

Observes every member of the population

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3
Q

Pros and cons of census

A

Pros:
- completely accurate result
Cons:
- expensive and time consuming
- cannot be used when testing process destroys item
- hard to process large quantities of data

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4
Q

Sample

A

Selection of observations taken from subset of population, used to find out info about whole population

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5
Q

Pros and cons of sampling

A

Pros:
- less time consuming and cheaper than census
- less data to process
- fewer people have to respond
Cons:
- data may not be accurate
- sample may not be large enough

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6
Q

Sampling frame

A

numbered / ordered list of sampling units

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7
Q

Simple random sampling

A

sampling where every unit has equal chance of being selected

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8
Q

Pros and cons of simple random sampling

A

Pros:
- No bias
- Easy and cheap
Cons:
- sampling frame needed
- not suitable for large sample size
- potentially expensive and time consuming

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9
Q

Systematic sampling

A

elements chosen sequentially from an ordered list

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10
Q

Pros and cons of systematic sampling

A

Pros:
- simple and quick
- suitable for large population
Cons:
- sampling frame needed
- could introduce bias

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11
Q

Stratified sampling

A

division of population into strata, and and random sampling from there

number in stratum = (stratum size / population size) x overall sample size

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12
Q

Pros and cons of stratified sampling

A

Pros:
- sample accurately reflects population
- guarantees proportional representation
Cons:
- time consuming to classify into strata
- sampling frame needed

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13
Q

Quota sampling

A

selecting a sample representative of population

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14
Q

Pros and cons of quota sampling

A

Pros:
- quick, easy, inexpensive
- representative of population
- no sampling frame needed
Cons:
- bias introduced
- time consuming to make more groups when increasing sample size
- time consuming to make groups

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15
Q

Opportunity sampling

A

taking sample of first available people at time of study

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16
Q

Pros and cons of opportunity sampling

A

Pros:
- easy
- inexpensive
Cons:
- dependent on researcher
- not representative

17
Q

Quantitative & qualitative data

A

Quantitative - number based
Qualitative - opinion based

18
Q

Types of variable

A

continuous - variable that can be any value
discrete - variable that can only have certain values

19
Q

Cloud cover

A
  • measured in oktas
  • measured in eights
  • 0 no cloud to 8 complete cloud
20
Q

Daily mean wind direction and speed

A

Beaufort scale
0 - calm - less than 1 knot
1 to 3 - light - 1to 10 knots
4 - moderate 11 to16 knots
5 - fresh - 17 to 21 knots

21
Q

Locations of cities in large data set

A

Jacksonville, Florida
Beijing, China
Perth, Australia,
Camborne, Cornwall
Hurn, S England
Heathrow, London
Leeming, N England
Leuchars, N Scotland