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A-Level Maths > Populations and Samples > Flashcards

Populations and Samples Flashcards

1
Q

What is a census

A

A census observes or measures every member of a population

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2
Q

What is a sample

A

A sample is a selection of observations taken from a whole subset of the population which is used to take information about the population as a whole

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3
Q

What are the advantages of a census

A

-It should give a completely accurate result

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4
Q

What are the disadvantages of a census

A
  • Time consuming and expensive
  • Cannot be used when the testing process destroys the item
  • Hard to process large quantity of data
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5
Q

What are the advantages of a sample

A
  • Less time consuming and expensive than a census
  • Fewer people have to respond
  • Less data to process than in a census
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6
Q

What are the disadvantages of a sample

A
  • The data may not be as accurate

- The sample may not be large enough to give information about small sub-groups of the population

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7
Q

What are three methods of random sampling

A
  • Simple random sampling
  • Systematic sampling
  • Stratified sampling
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8
Q

What is a simple random sample

A

A simple random sample of size ‘n’ is one where every sample of size ‘n’ has an equal chance of being selected

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9
Q

What is a systematic sample

A

In a systematic sample, the required elements are chosen at regular intervals from an ordered list

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10
Q

What is a stratified sample

A

In stratified sampling, the populations is divided into mutually exclusive strata (men and women etc etc) and a random sample is taken from each

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11
Q

What is the equation for a systematic sample

A

Population/sample size = Intervals

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12
Q

What is the equation for a stratified sample

A

Number sampled in a stratum = (No in stratum/No in population) * overall sample size

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13
Q

What are the advantages of simple random sampling

A
  • Free of bias
  • Easy and cheap to implement for small populations and sample sizes
  • Each sampling unit has a known and equal chance of selection
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14
Q

What are the disadvantages of simple random sampling

A
  • Not suitable when the population size or the sample size is large
  • A sampling frame is needed
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15
Q

What are the advantages of systematic sampling

A
  • Simple and quick to use

- Suitable for large samples and large populations

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16
Q

What are the disadvantages of systematic sampling

A
  • Population must be clearly classified into distinct strata

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

17
Q

What are the advantages of stratified sampling

A
  • Sample accurately represents the population structure

- Guarantees proportional representation of groups within a population

18
Q

What are the disadvantages of stratified sampling

A
  • Population must be classified into distinct strata

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

19
Q

What are the two types of non-random sampling

A

Quota sampling or opportunity sampling

20
Q

What is quota sampling

A

In quota sampling, an interviewer or researcher selects a sample that reflects the characteristics of the whole population

21
Q

What is opportunity sampling

A

Opportunity sampling consists of taking the sample from people who are available at the time the study is carried out and who fit the criteria you are looking for

22
Q

What are the advantages of quota sampling

A
  • Allows a small sample to still be representative of the population
  • No sampling frame required
  • Quick, easy and inexpensive
  • Allows for easy comparison between different groups within a population
23
Q

What are the disadvantages of quota sampling

A
  • Non-random sampling can introduce bias
  • Population must be divided into groups, which can be costly or inaccurate
  • Increasing scope of study increases the number of groups, which adds time and expense
  • Non-responses are not recorded as such
24
Q

What are the advantages of opportunity sampling

A
  • Easy to carry out

- Inexpensive

25
Q

What are the disadvantages of opportunity sampling

A

Unlikely to provide a representative sample

-Highly dependent on individual researcher

26
Q

What is quantitative data

A

Data associated with numerical observations e.g shoe sizes

27
Q

What is qualitative data

A

Data associate with non-numerical observations e.g Hair colour

28
Q

What is continuous data

A

A variable that can take any value within a given range e.g time 2 seconds, 2.1 seconds, 2.01 seconds

29
Q

What is discrete data

A

A variable that can only take a few specific values in a given range e.g number of people in a family, can’t have 3.4 members

A-Level Maths (3 decks)

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