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A-level Maths > Sampling > Flashcards

Sampling Flashcards

1
Q

What is a population?

A
  • Is the whole set of items that are of interest.
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2
Q

What is a sample?

A
  • Some subset of a population intended to represent the population
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3
Q

What is a sampling unit?

A
  • Each individual thing in the population that can be sampled is known as a sampling unit.
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4
Q

What is a sampling frame?

A
  • Sampling units of a population are individually named or numbered to form a list called the sampling frame.
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5
Q

What is a cenus?

A
  • When the data is collected from the whole population
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6
Q

What are the advantages and disadvantages of a census?

A

ADVANTAGES:
- Gives a completely accurate result

DISADVANTAGES
- Expensive and time consuming
- Cannot be used in testing until destruction
- Large volume of data to process

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7
Q

What are the advantages and disadvantages of a sample?

A

ADVANTAGES
- Cheaper and less time consuming
- Less data to process
- Can be used to test until destruction

DISADVANTAGES
- Not accurate
- Doesn’t represent minorities

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8
Q

What is simple random sampling?

A
  • It is when every sample has an equal chance of being selected
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9
Q

What is the method for simple random sampling?

A
  • In sampling frame each item has an identifying number
  • Use a random number generator to chose numbers in the correct range.
  • The corresponding item to the selected number will be part of the sampling frame.
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10
Q

What are the advantages and disadvantages of simple random sampling?

A

ADVANTAGES
- Easy and cheap
- Each number has a known equal chance of being selected so truly random

DISADVANTAGES
- Not suitable when population size is large
- Sampling frame needed

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11
Q

What is systematic sampling?

A
  • Required objects are chosen at regular intervals in an ordered list.
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12
Q

What is the method for systematic sampling?

A
  • Allocate each item in the population a number.
  • Divide the population size by the sample size to find k
  • Use a random number generator to decide the starting number between 1 and k
  • Select every kth person in the list to become part of the sampling frame.
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13
Q

What are the advantages and disadvantages of systematic sampling?

A

ADVANTAGES
- Simple and quick
- Suitable for large population sizes

DISADVANTAGES
- Sampling frame needed
- Can introduce bias if sampling frame not random

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14
Q

What is a strata?

A
  • When the population is split into distinct groups such as age ranges
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15
Q

What is quota sampling ?

A
  • Population divided into groups according to characteristics of interest , then determine size of each group (quota ) in sample to reflect proportions within the population
  • Samples are chosen within each group via suitable means, until the ‘quota’ for each group is filled.
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16
Q

What are the advantages of quota sampling?

A
  • Allows small sample to be representative
  • No sampling frame required
  • Quick, easy and inexpensive
  • Allows for easy comparison between different groups in population
17
Q

What are the disadvantages of quota sampling?

A
  • no random and therefore can be bias
  • separating into groups can be expensive and inaccurate
  • increasing scope of study increase umber of groups adding cost
  • non-response are not recorded
18
Q

What is convenience sampling?

A
  • Sample taken from people who are available at the time of study, who meet criteria
19
Q

What are the advantages and disadvantages of opportunity sampling?

A

ADVANTAGES
- Easy to carry out
- Inexpensive
DISADVANTAGES
- Unlikely to provide a representative sample
- Highly dependent on individual researcher

20
Q

What are all the different types of data?

A
  • Qualitive -> non-numerical values
  • Quantitative -> numerical values
    Discrete -> Can only take specific values
    Continuous -> Can take any decimal value
21
Q

What is variance?

A
  • Measure of spread that takes all values into account
  • Variance is the average squared distance from the mean
  • (Standard deviation)^2 = sum of x^2/n - mean^2
22
Q

Binomial distribution qualifiers

A
  • There are fixed number of trials
  • There are two possible outcomes
  • There is a fixed probability of success
  • The trials are independent of each other

A-level Maths (3 decks)

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