Population & Sample Flashcards

1
Q

What is the target population?

A

Population which we aim to apply our results to

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2
Q

What is the source population?

A

Sampling frame - list of accessible members of target population

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3
Q

What is the eligible population?

A

Large fraction of the source population will be excluded when study criteria are applied i.e. ineligible

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4
Q

Who are study entrants?

A

When eligible population are approached, large portion will be excluded due to e.g. lack of consent, non-response etc.
Those left are the study entrants

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5
Q

Who are the study participants?

A

Not all the study entrants will complete study requirements or be available for follow-up. The remnants are in this group.

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6
Q

What is sampling error?

A

Difference between outcome value estimated from sample and true-whole population outcome one might get by including everyone in the population

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7
Q

What does sampling error depend on?

A

Sampling technique
Sample size

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8
Q

What type of sampling reduces sampling error?

A

Random sampling

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9
Q

What sample sizes produce less sampling error?

A

Large sample sizes

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10
Q

What is non-probability sampling

A

Non-random sampling

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11
Q

Disadvantages of non-random sampling

A

Generalisability is weaker

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12
Q

Types of non-random sampling

A

Quota
Convenience
Volunteer
Snowball
Consecutive
Purposive

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13
Q

What is quota sampling?

A

Sampling frame divided into subgroups called strata based on selected variables
Non-random sample picked from each stratum

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14
Q

What is snowball sampling?

A

One identified subject helps to locate another subject

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15
Q

What is consecutive sampling?

A

Case series of consecutive patients with conditions of interest

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16
Q

What happens in consecutive sampling

A

All patients who present to research site at time of study are included

17
Q

What types of studies are purposive sampling used in?

A

Qualitative

18
Q

What happens in purposive sampling?

A

Subjects picked deliberately based on pre-requisite objectives

19
Q

Types of purposive sampling

A

Extreme
Critical case
Theoretical purposive

20
Q

What happens in extreme sampling?

A

Cases representing two extremes are recruited

21
Q

What happens in critical case sampling?

A

Subjects expected to yield maximum information are selected

22
Q

What happens in theoretical purposive sampling?

A

Subsequent recruitment depends on those categories that emerged from data so far

23
Q

Another name for systematic sampling

A

Interval sampling

24
Q

What happens in interval sampling?

A

Every nth item from sampling frame is selected

25
Q

Difference between random and non-random sampling

A

In random sampling, each individual in the population has an equal chance of being chosen