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AS Maths > Statistics Chapter 1 > Flashcards

Statistics Chapter 1 Flashcards

1
Q

What is a Population

A

The whole set of items of interest

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2
Q

What is a Sample

A

A subset of the population

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3
Q

What is a sampling unit

A

Each individual thing in the population that can be sampled

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4
Q

What is a sampling frame

A

Named/Numbered units of a population to form a list

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5
Q

What is a census?

A

Where data is collected from the entire population

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6
Q

What are the advantages and disadvantages of a census?

A

+ Should give a completely accurate result

  • Time consuming
  • Expensive
  • Testing involves destruction
  • Large volume of data to test
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7
Q

What are the benefits of a sample compared to a census?

A

+ Cheaper
+ Quicker
+ Less data to process

  • Data may not be accurate
  • Data may not be large enough to represent small subgroups
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8
Q

How could you improve a sample?

A

Use a larger sampling size

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9
Q

What is a simple random sample?

A

A sample where every sampling unit has an equal chance of being selected

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10
Q

Explain how you would carry out a simple random sample

A

1) Assign each item a number
2) Use a random number generator (such as random function on a calculator or spreadsheet) to select numbers
3) The sampling units corresponding to these numbers become the sample

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11
Q

What are the advantages of a simple random sample?

A

+ Bias free
+ Easy and cheap
+ Unit have an equal chance of selection

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12
Q

What are the disadvantages of a simple random sample?

A
  • Not suitable for a large population

- Requires a sampling frame (which may not be possible)

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13
Q

What is systematic sampling?

A

Required elements are chosen at regular intervals in ordered list.

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14
Q

Explain how you could carry out a systematic sample?

A

1) Assign each item a number
2) k = population size/sample size
3) Randomly select the first number using a random number generator between 1 and k
4) Then choose every kth item after this

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15
Q

What are the advantages of a systematic sample?

A

+ Simple, quick

+ Suitable for large populations

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16
Q

What are the disadvantages of a systematic sample?

A
  • Need sampling frame

- Can introduce bias is the sampling frame is not random

17
Q

What is stratified sampling?

A

Where the population is divided into groups (strata) and a simple random sample carried out in each group.

18
Q

Explain how you would carry out a stratified sample

A

1) Calculate the proportion of each strata to be sampled (sample size/population) x strata size
2) Carry out a simple random sample for each strata:
i) Assign a number to each unit
ii) Use a random number generator (such as random function on a calculator or spreadsheet) to select numbers
iii) The sampling units corresponding to these numbers become the sample

19
Q

What are the advantages of a stratified sample?

A

+ Reflects the structure of the population

20
Q

What are the disadvantages of a stratified sample?

A
  • Population must be classified into strata (not always possible)
  • Has the same issues of a simple random sample
21
Q

What is quota sampling?

A

A quota is set for each group in a population proportionally. Sampling units are then selected until the quota for each group is filled.

22
Q

How would you carry out quota sampling?

A

1) Calculate the proportion of each strata to be sampled (sample size/population) x strata size
2) Select sampling units until each quota is filled.

23
Q

What are the advantages of quota sampling?

A

+ No sampling frame is required
+ Allows a small sample to be representative of a population
+ Quick, easy and inexpensive
+ Easy comparison between different groups

24
Q

What are the disadvantages of quota sampling?

A
  • Non random sampling can introduce bias
  • Population must be separated into groups which could be costly/inaccurate
  • Non-responses are not recorded
25
Q

What is opportunity sampling?

A

Sample taken from people who are available at time of study, who meet criteria.

26
Q

What are the advantages of opportunity sampling?

A

+ Easy to carry out.

+ Inexpensive.

27
Q

What are the disadvantages of opportunity sampling?

A
  • Unlikely to provide a representative sample.

- Highly dependent on individual researcher.

AS Maths (2 decks)

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