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Maths Flashcards > 3.1 Sampling > Flashcards

3.1 Sampling Flashcards

1
Q

Population

A

The set of things you are interested in

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2
Q

Sample

A

The subset of the population

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3
Q

Parameter

A

The number that describes the entire population

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4
Q

Statistic

A

A number taken from a single sample

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5
Q

Census

A

Observes or measures every member of a population

It can be a survey/experiment

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6
Q

Adv and Disadv of census

A

Adv
- give a completely accurate result

Disadv

  • time consuming
  • expensive
  • hard to process large quantity of data
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7
Q

Adv and disadv of sample

A

Adv

  • less time consuming
  • less expensive
  • fewer people have to respond
  • less data to process compared to census

Disadv

  • data may not be accurate
  • sample may not be large enough to give info about small sub-groups of the population
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8
Q

Sampling unit

A

Individual units of a population

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9
Q

Sampling frame

A

This is where sampling units of a population are individually named or numbered to form a list

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10
Q

Different types of sampling

A
  1. Simple random sampling
  2. Systematic sampling
  3. Stratified sampling
  4. Opportunity sampling
  5. Quota sampling
  6. Cluster sampling
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11
Q

Simple random sampling

A

Every member of the population is equally likely to be chosen. (A simple random sample of size n is one where every sample of size n has an equal chance of being selected)

Eg
Allocate each member in population a number and then use random numbers to choose a sample of desired size

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12
Q

Systematic sampling

A

Find a sample of size n from a population of size N by taking one member from the first k members of the population at random and then selecting every kth member after that.

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13
Q

Equation for systematic sampling

A

K = N/n

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14
Q

Stratified sampling

A

When you know you want distinct groups to be represented in your sample, split the population into these distinct groups and then sample within each group in proportion to its size.

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15
Q

Equation for stratified sampling

A
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16
Q

Adv and disadv of simple random sampling

A

Adv

  • free of bias
  • easy and cheap to implement for small populations
  • each sampling unit has a known and equal chance of selection

Disadv

  • not suitable when the population/sample size is large
  • a sampling frame is needed
17
Q

Adv and disadv of systematic sampling

A

Adv

  • simple and quick to use
  • suitable for large samples and large populations

Disadv

  • a sampling frame is needed
  • can introduce bias if the sampling frame is not random
18
Q

Adv and disadv of stratified sampling

A

Adv

  • sample accuracy reflects the population structure
  • guarantees proportional representation of groups within population

Disadv

  • population must be clearly classified into distinct strata
  • selection within each stratum suffers from the same disadvantages as simple random sampling
19
Q

Quota sampling

A

When you know you want distinct groups to be represented in your sample, decide how many members of each group you wish to sample in advance and use opportunity sampling until you have a large enough sample for each group.

20
Q

Opportunity sampling

A

Take samples from members of the population you have access to until you have a sample of the desired size.

21
Q

Cluster sampling

A

Split the population into clusters that you expect to be similar to each other, then take a sample from each of these clusters.

22
Q

Adv and disadv of quota sampling

A

Adv

  • allows a small sample to still be representative of the pop
  • no sampling frame required
  • quick and easy and inexpensive
  • allows for easy comparison between diff groups within a population

Disadvantage

  • non-random sampling can introduce bias
  • pop must be divided into groups, which can be costly/inaccurate
  • non-responses are not recorded as such
23
Q

Adv and disadv of opportunity sampling

A

Adv

  • easy to carry out
  • inexpensive

Disadv

  • unlikely to provide a representative sample
  • highlight dependent on individual researcher
24
Q

Quantitative variable/data

A

Variables or data associated with numerical observations

25
Q

Qualitative variable/data

A

Variables or data associated with non-numerical observations

26
Q

Continuous variable/data

A

A variable/data that can take any value in a given range

Eg height

27
Q

Discrete variable/data

A

Variable/data that can only take specific values in a given range
Eg feet size, blood group

Maths Flashcards (35 decks)

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