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Maths > Statistics- Data Collection (1) > Flashcards

Statistics- Data Collection (1) Flashcards

1
Q

Population

A

Whole set of items that are of interest

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2
Q

Census

A

Observes/measures each member of a population

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3
Q

Sample

A

Selection of observations taken from a subset of the population, used to find information about the whole population

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4
Q

Census Advantages

A

Completely accurate

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5
Q

Census Disadvantages

A
  • Time consuming and expensive
  • Cannot be used if the testing process destroys the item
  • Hard (or impossible) to process large quantities of data
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6
Q

Sample Advantages

A
  • Less time consuming and less expensive than a census
  • Fewer responses needed
  • Less data to process
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7
Q

Sample Disadvantages

A
  • Data may not be accurate

- Sample may not be large enough to reflect all subsets

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8
Q

Sampling units

A

Individual units of a population

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9
Q

Sampling frame

A

List of individually numbered or named sampling units

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10
Q

3 main random sampling methods

A
  • Simple random
  • Systematic
  • Stratified
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11
Q

Simple random sampling

A

Sample is chosen randomly using a random number generator

-requires a sampling frame to be set up

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12
Q

Systematic sampling

A

Every nth member of the population is chosen from an ordered list where

  • n=population size/sample size
  • first element should be a random number between 1 and n
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13
Q

Stratified sampling

A

Population is divided into mutually exclusive strata and a random sample is taken from each
-proportion of each strata should be the same

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14
Q

Stratified sampling formula

A

Number sampled in a stratum= (number in stratum/ number in population)*overall sample size

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15
Q

Simple random sampling ADV

A
  • Free of bias
  • Easy and cheap to implement for small populations and samples
  • Each sampling unit has a knows and equal chance of selection
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16
Q

Simple random sampling DISADV

A
  • Not suitable when there is a large population or sample size
  • A sampling frame is needed
17
Q

Systematic sampling ADV

A
  • Simple and quick

- Suitable for large samples and populations

18
Q

Systematic sampling DISADV

A
  • A sampling frame is needed

- Can introduce bias if the sampling frame is not random (two people together are unlikely to be selected)

19
Q

Stratified sampling ADV

A
  • Accurately reflects population structure

- Guarantees proportional representation of groups in the population

20
Q

Stratified sampling DISADV

A
  • Population must be clearly classified into distinct strata

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

21
Q

2 main non-random sampling methods

A
  • Quota

- Opportunity

22
Q

Quota Sampling

A

An interviewer or researcher selects a sample that reflects the characteristics of the whole population

23
Q

Opportunity Sampling

A

Sampling the people who are available whilst the study is carried out and fit criteria

24
Q

Quota sampling ADV

A
  • Allows a small sample to represent the whole population
  • No sampling frame needed
  • Quick, easy, inexpensive
  • Allows for easy comparison between different groups
25
Q

Quota sampling DISADV

A
  • Non random= bias
  • Population must be divided into groups
  • Increasing scope of study increases the number of groups, take time and money
  • Non-responses aren’t recorded as such
26
Q

Opportunity sampling ADV

A
  • Easy to carry out

- Inexpensive

27
Q

Opportunity sampling DISADV

A
  • Unlikely to provide a representative sample

- Dependent on individual researcher

28
Q

Quantitative variable

A

Data associated with numerical observations

29
Q

Qualitative variable

A

Data associated with non-numerical observations

30
Q

Continuous variable

A

A variable that can take any value in a given range

31
Q

Discrete variable

A

A variable that can only take specific values in a given range

32
Q

Class

A

The groups data is presented in in a grouped frequency table

33
Q

Class boundaries

A

Max and min values in each class

34
Q

Midpoint

A

Average of the class boundaries

35
Q

Class width

A

Difference between upper and lower boundaries

Maths (11 decks)

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