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A Level Maths (Edexcel) EVERYTHINGG > Data Collection > Flashcards

Data Collection Flashcards

1
Q

Population

A

The whole set of items that are of interest

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2
Q

Census

A

Measures or observes every member of a population

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3
Q

Sample

A

A selection of observations taken from a subset of population and used to find out more information about the population as a whole

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4
Q

Advantages of a Census

A
  • Results should be completely accurate
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5
Q

Disadvantages of a Census

A
  • Time consuming and expensive
  • Cannot be used when testing destroys process
  • Hard to process large quantity of data
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6
Q

Advantages of Sample

A
  • Less time consuming and cheaper
  • Fewer people have to respond
  • Less data needs to be processed
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6
Q

3 types of Random Sampling:

A
  • Simple Random Sampling
  • Systematic Sampling
  • Stratified Sampling
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7
Q

What are Sampling units?

A

Individual units of a population that are named and numbered to form sampling frame

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7
Q

Disadvantages of Sample

A
  • Data may not be accurate
  • Sample may not be large enough to give information about small subgroups of the population
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7
Q

What is Random Sampling?

A
  • Where each member of the population has an equal chance of being selected
  • The sample should be representative of the population and bias should be removed
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8
Q

What is Simple random sampling?

A

Where every sampling unit in the sampling frame has an equal chance of being selected

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9
Q

How to carry out Simple Random Sampling?

A
  • Allocate a number between 1 and N to each sampling unit, within the sampling frame
  • Use a random number generator or method of lottery sampling to select X numbers between 1 and N
  • Units corresponding to these numbers become the sample
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10
Q

Advantages of Simple Random Sampling

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

Disadvantages of Simples Random Sampling

A
  • Not suitable for large samples and populations
  • Sampling frame is needed
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12
Q

What is Systematic Sampling?

A

Where required elements are chosen at regular intervals in ordered list

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13
Q

How to carry out a Systematic sample?

A
  • Divide the population size of by the sample size to obtain the interval of k
  • Then use a random generator to obtain a unit between 1 and k
  • Start with the unit obtained and go up in the interval you worked out
14
Q

Advantages of Systematic Sampling

A
  • Simple and quick to use
  • Suitable for large samples and large populations
15
Q

Disadvantages of Systematic Sampling

A
  • Bias introduced if sampling frame is not random
  • A sampling frame is needed
16
Q

What is Stratified Sampling?

A
  • Where the population is divided into strata and a simple random sample is carried out in each group
  • Used when sample is large and population is naturally divided into groups
17
Q

How to carry out a Stratified Sample?

A
  • Find the total number of population
  • Obtain the same proportion from each strata by dividing sample size by population size and then multiplying answer by the sample size given in question
  • Number the workers in each strata
  • Use a random number generator to produce the required quantity of random numbers
18
Q

Advantages of Stratified Sampling

A
  • Sample accurately reflects population structure
  • Proportional representation of groups within population
19
Q

Disadvantages of Stratified Sampling

A
  • Population must be clearly classified into distinct strata
  • Sampling frame needed
20
Q

What are the two types of non random sampling:

A
  • Quota sampling
  • Opportunity sampling
21
Q

What is Quota sampling?

A

Where a researcher selects a sample that reflects the characteristics of the whole population

22
Q

Advantages of Quota Sampling

A
  • Allows a small sample to be representative of the population
  • Quick, easy and inexpensive
  • Easy comparison between different groups within a population
23
Q

Disadvantages of Quota Sampling

A
  • Can introduce bias
  • Population must be divided into groups which can be costly or inaccurate
  • Increasing scope of study increases number of groups and, which adds time and expenses
24
Q

What is Opportunity sampling?

A

Where sample is taken from people who are available at the time of study and who fits the criteria they are looking for

25
Q

Advantages of Opportunity sampling

A
  • Easy and inexpensive
26
Q

Disadvantages of Opportunity Costs

A
  • Unlikely to provide a representative result
  • Highly dependent on individual research
27
Q

What is a continuous variable?

A
  • A variable that can take any value in a given range
28
Q

What is a discrete variable?

A
  • A variable that can only take specific values
29
Q

What is the class width?

A

The difference between upper and lower class boundaries

A Level Maths (Edexcel) EVERYTHINGG (17 decks)

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