Statistics definitions Flashcards

1
Q

What is a population?

A

The whole set of items that are of interest.

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2
Q

What does a census do?

A

It measures every member of a population.

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3
Q

What is a sample?

A

A selection of observations taken from a subset of the population which is used to find out information about the population as a whole.

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4
Q

What are sampling units?

A

Individual units of a population.

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5
Q

What is a sampling frame?

A

A list of individually named or numbered sampling units of a population.

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6
Q

What are the three methods of random sampling?

A
  • Simple random sampling
  • Systematic sampling
  • Stratified sampling
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7
Q

What is a simple random sample?

A

One where every sample has an equal chance of being selected.

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8
Q

What is a systematic sample?

A

One where the required elements are chosen at regular intervals from an ordered list.

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9
Q

What is a stratified sample?

A

One where the population is ordered into mutually exclusive strata and a random sample is taken from each.

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10
Q

What are the advantages of simple random sampling?

A
  • Free of bias
  • Easy and cheap for small populations and samples
  • Each sampling unit has a known and equal chance of selection
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11
Q

What are the disadvantages of simple random sampling?

A
  • Not suitable when the population or sampling size is large

- A sampling frame is needed

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12
Q

What are the advantages of systematic sampling?

A
  • Simple and quick

- Suitable for large samples and populations

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13
Q

What are the disadvantages of systematic sampling?

A
  • A sampling frame is needed

- It can introduce bias if the sampling frame is not random

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14
Q

What are the advantages of stratified sampling?

A
  • Sample accurately reflects the population structure

- Guarantees proportional representation of groups within a population

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15
Q

What are the disadvantages of stratified sampling?

A
  • Population must be clearly classified into distinct strata

- Selection within each stratum suffers from the same disadvantages as simple random sampling

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16
Q

What are the two types of non-random sampling?

A

Quota sampling and opportunity sampling.

17
Q

What is a quota sample?

A

One where an interviewer or researcher selects a random sample that reflects the characteristics of the whole population.

18
Q

What is an opportunity sample?

A

One where a sample is taken from people who are available at the time the study is carried out and people who fit the criteria you are looking for.

19
Q

What are the advantages of quota sampling?

A
  • Allows a small sample to still be representative of the population
  • No sampling frame needed
  • Quick easy and inexpensive
  • Allows for easy comparison between different groups within a population
20
Q

What are the disadvantages of quota sampling?

A
  • Can introduce bias
  • Population must be divided into groups which can be costly or inaccurate
  • Non-responses are recorded as such
21
Q

What are the advantages of opportunity sampling?

A
  • Easy to carry out

- Inexpensive

22
Q

What are the disadvantages of opportunity sampling?

A
  • Unlikely to provide a representative sample

- Highly dependent on individual researcher

23
Q

What is a continuous variable?

A

One that can take any value in a given range.

24
Q

What is a discrete variable?

A

One that can only take specific values in a given range.