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AQA Mathematics > Statistics - Data collection > Flashcards

Statistics - Data collection Flashcards

1
Q

What is a population?

A

The whole set of items that are of interest

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2
Q

What is a census?

A

A survey that observes/measures every member of a population

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3
Q

What is a sample?

A

A selection of observations taken from a subset of a population which is used to find out info about the whole population

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4
Q

What is the advantage of a census?

A

Should give a completely accurate result

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5
Q

What are the disadvantages of a census?

A

Time consuming & expensive
Hard to process large quantities of data
Cannot be used when testing process destroys item

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6
Q

What are the advantages of taking a sample?

A

Less time consuming & expensive than a census
Fewer people have to respond
Less data to process

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7
Q

What are the disadvantages of taking a sample?

A

Data may not be accurate

Sample maybe not large enough to represent all small sub-groups in the population

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8
Q

What happens as the sample size increase?

A

The more accurate it is

More representative of the sample

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9
Q

What is the individual units of a population called?

A

Sampling units

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10
Q

What are done to sampling units in order to distinguish them?

A

They are individually named or numbered to form a list

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11
Q

What is a statistic?

A

A value taken from a single sample

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12
Q

What is a sampling frame?

A

A list of the sample units

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13
Q

What happens in random sampling?

A

Each member of the population has an equal chance of being selected

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14
Q

What are the advantages of using random sampling?

A

Representative of the population

Removes bias

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15
Q

What are the three methods of random sampling?

A

Simple random sampling
Systematic sampling
Stratified sampling

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16
Q

How can you perform simple random sampling?

A

Number each sampling unit

Random number generator or numbers put into a “hat” and chosen at random

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17
Q

What are the advantages of simple random sampling?

A

Free of bias
Easy and cheap for small populations/samples
Each sampling unit has a known/equal chance of selection

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18
Q

What are the disadvantages of simple random sampling?

A

Not suitable when population/sample size is large

Sampling frame is needed

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19
Q

What is systematic sampling?

A

Required elements are chosen at regular intervals from an ordered list
E.g Data taken every nth value

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20
Q

What are the advantages of systematic sampling?

A

Simple and quick to use

Suitable for large samples/populations

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21
Q

What are the disadvantages of systematic sampling?

A

Sampling frame is needed

Can introduce bias if sampling frame is not random

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22
Q

What is stratified sampling?

A

Population is divided into mutually exclusive strata, and a random sample is taken from each
Strata example - male & female

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23
Q

What rules should be followed for obtaining strata?

A

Proportion of each strata should be the same

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24
Q

What is the formula to calculate the number of people should be sampled from each strata?

A

Number sampled in strata = (number in strata / number in population) x overall sample size

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25
Q

What are the advantages of stratified sampling?

A

Sample accurately reflects the population structure

Guarantees proportional representation of groups within a population

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26
Q

What are the disadvantages of stratified sampling?

A

Population must be clearly classified into distinct strata

Selection within each stratum has disadvantages of simple random sampling

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27
Q

What are the two types of non-random sampling?

A

Quota sampling

Opportunity sampling

28
Q

What is quota sampling?

A

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

29
Q

How is quota sampling done?

A

Population is divided into groups by an interviewer due to characteristics
Continues until quota is full

30
Q

What happens with quota sample sizes?

A

Size of each group determines proportion of sample that should have that characteristic
Quotas will have a limit - if full the person’s data is dismissed

31
Q

What are the advantages of quota sampling?

A

No sampling frame required
Quick, easy and inexpensive
Small sample still representative of population
Allows easy comparison between different groups

32
Q

What are the disadvantages of quota sampling?

A

As non-random it introduces bias
Population division can be costly or inaccurate
Non-responses are not recorded
Increases groups so adds time and expensive

33
Q

What is opportunity sampling?

A

Taking the sample from people who are available at the time the study is carried out and who fit the criteria you are looking for

34
Q

What are the advantages of opportunity sampling?

A

Easy to carry out

Inexpensive

35
Q

What are the disadvantages of opportunity sampling?

A

Highly dependent on individual researches

Unlikely to provide representative sample

36
Q

What is opportunity sampling also known as?

A

Convenience sampling

37
Q

What is quantitative variables/data?

A

Data/variables associated with numerical observations

38
Q

What is qualitative variables/data?

A

Data/variables associated with non-numerical observations

39
Q

What is a continuous variable?

A

A variable that can be given in any range

E.g 2 seconds, 2.3 s, 2.02 s

40
Q

What is a discrete variable?

A

A variable that can only be specific values

E.g can’t have 2.65 people

41
Q

What are the groups in grouped frequency tables called?

A

Classes

42
Q

What face value data can be found using a grouped frequency table?

A 
Class boundaries tell you max and min values in the class
Midpoint is the average of the class boundaries
Class width is the difference between higher and lower class boundaries
43
Q

What large data sets will be provided?

A

Data about the weather, location, about different places around the world

44
Q

What is the daily mean temperature?

A

°C

Average of hourly temp readings

45
Q

What is the daily total rainfall?

A

Includes solid precipitation
Melted before being included in measurements
Less than 0.05mm recorded as “trace” or “tr”

46
Q

What is daily total sunshine?

A

Recorded to nearest tenth of an hour

47
Q

What is the daily mean wind direction and windspeed?

A

Knots, averaged over 24 hours
Directions given as bearings & compass directions
Mean windspeed also in Beaufort scale

48
Q

What is a knot?

A

1 kn = 1.15 mph

49
Q

What is the daily max gust?

A

Highest instantaneous wind speed recorded in knots

50
Q

What is the daily max relative humidity?

A

% air saturation with water

Above 95% can be misty/foggy

51
Q

What is daily mean cloud cover?

A

Measured in oktas - eighths of sky covered by cloud

Goes from 0-8

52
Q

What is daily mean visibility?

A

Greatest distance an object can be seen in daylight

Measured in decameters (Dm)

53
Q

What is daily mean pressure measured in?

A

Hectopascals (hPa)

54
Q

What is a finite and infinite population?

A

Finite - can practically be counted

Infinite - cannot be counted practically

55
Q

What is cluster sampling?

A

Divide population into clusters
Randomly select clusters based on sample size
Either use all in cluster or randomly sample

56
Q

What are the advantages in cluster sampling?

A

More practical in some situations

Incorporate other methods into it

57
Q

What are the disadvantages in cluster sampling?

A

Less representative as only some clusters sampled

Not always possible to separate into clusters in natural ways

58
Q

What is self-selection/volunteer sampling?

A

People choose to be part of the study after advertisement to whole population
Either use all who respond or take sample of them

59
Q

What are the advantages of self-selection sampling?

A

Little time or effort for sample members
Volunteers are less-likely to not respond
Could be only way to get people to take part

60
Q

What are the disadvantages of self-selection sampling?

A

Trends could be present within the population that responds

61
Q

What does n/a mean?

A

Not available

62
Q

What is 0 on the Beaufort scale?

A

Calm

Less than 1 knot

63
Q

What is 1-3 on the Beaufort scale?

A

Light

1-10 knots

64
Q

What is 4 on the Beaufort scale?

A

Moderate

11-16 knots

65
Q

What is 5 on the Beaufort scale?

A

Fresh

17-21 knots

AQA Mathematics (68 decks)

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