Sampling Flashcards

1
Q

Define sampling

A

Taking data from a small part of a large population and then scale up to fit the total population. Researchers use a sampling method to prevent bias.

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2
Q

What is random sampling?

A

Locations chosen by chance.

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3
Q

Outline the strengths of random sampling

A

Removes human bias when selecting of sites/population - where may want to select sites that confirm hypotheses. Everything has an equal chance of being selected.

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4
Q

Outline the weaknesses of random sampling

A

If sample size is small may it may be unrepresentative result.
No guarantee that the sample will be representative of the population.

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5
Q

What is systematic sampling?

A

Locations chosen at equal intervals.

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6
Q

Outline the strengths of systematic sampling

A

Accurately shows continuous changes e.g. velocity across a river/ people along a road.
Can be more accurate than random sampling as avoids the chance that a random sample only selects from one part of a population.
Quick/ convenient because you have a system to follow.
Representative data of what’s happening at the time.
Unlikely to miss variations/anomalies as cover whole area.

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7
Q

Outline the weaknesses of systematic sampling

A

Can pick bias as sampling every 50 cm or so may be crossing points for pedestrians etc.
Access at regular intervals may be impossible (e.g. due to private land/ unsafe)

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8
Q

What is stratified sampling?

A

Total population divided into smaller groups (strata) an equal proportion to those in the total population are used.

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9
Q

Outline the strengths of stratified sampling

A

Ensures all areas/types/categories are represented.

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10
Q

Outline the weaknesses of stratified sampling

A

Difficult to know which subsets of data to include without a pilot study or prior use of secondary data.
Access to specific sites may be difficult.

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11
Q

What is opportunistic sampling?

A

Selecting anyone who is available and willing to take part.

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12
Q

Outline the strengths of opportunistic sampling

A

Less time consuming; easiest method to use. Allows access to sites that are safe/on public land.

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13
Q

Outline the weaknesses of opportunistic sampling

A

BIASED. Data is unlikely to accurately represent the population.

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14
Q

What is transect sampling?

A

Data collected along a line.

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15
Q

Outline the strengths of transect sampling

A

Show continuous change.

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16
Q

Outline the weaknesses of transect sampling

A

Can pick bias in transect location.