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Maths > Large Data Set > Flashcards

Large Data Set Flashcards

1
Q

advantage of a census

A

it should give a completley accurate result

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2
Q

disadvantages of a census

A
  • time consuming
  • cannot be used when the testing process destroys the item
  • hard to process large quantity data
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3
Q

advantages of a sample

A
  • less time consuming and expensive than a census
  • fewer people have to respond
  • less data to process than in a census
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4
Q

disadvantages of a sample

A
  • the data may not be as accurate
  • the sample may not be large enough to give information about small sub-groups of the population
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5
Q

define census

A

observers of measures every member of a population

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6
Q

define sample

A

a selection of observations taken from a subset

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7
Q

what are sampling units

A

individual units of a population

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8
Q

what is a sampling frame

A

often sampling units of a population are individually named or numbered to form a list

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9
Q

what are the three methods of random sampling

A

1.simple random
2. systematic
3. stratified

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10
Q

what is simple random sampling

A

where every sample of size n has an equal chance of being selected

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11
Q

what is systematic random sampling

A

the required elements are chosen at regular intervals from an ordered list

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12
Q

what is stratified sampling

A

the population is divided into mutually exclusive strata (males and females, for example) and a random sample is taken from each

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13
Q

advantages of simple random sampling

A
  • free of bias
  • easy and cheap to implement for small populations and small samples
  • each sampling unit has a known and equal chance of selection
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14
Q

disadvantages of simple random sampling

A
  • not suitable when the population size or the sample size is large as it is potentially time consuming, disruptive and expensive
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15
Q

advantages of systematic sampling

A
  • simple and quick to use
  • suitable for large samples and large populations
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16
Q

disadvantages of systematic sampling

A
  • a sampling frame is needed
  • it can introduce bias if the sampling is not random
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17
Q

advantages of stratified sampling

A
  • sample accurately reflects the population and structure
  • guarantees proportional representation of groups with a population
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18
Q

disadvantages of stratified sampling

A
  • population must be clearly classified into distinct strata
  • selection within each stratum suffers from the same disadvantages as simple random sampling
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19
Q

2 examples of non-random sampling

A
  1. quota
  2. opportunity
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20
Q

what is quota sampling

A

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

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21
Q

advantages of quota sampling

A
  • allows a small sample to still be representative of the population
  • no sampling frame required
  • quick, easy and inexpensive
  • allows for easy comparison between different groups within a population
22
Q

disadvantages of quota sampling

A
  • non-random sampling can introduce a bias
  • population must be divided into groups, which can be costly or inaccurate
  • increasing scope of study increases number of groups, which adds time and expense
  • non-responses are recorded as such
23
Q

what is opportunity sampling

A
  • consits of 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
24
Q

advantages of opportunity sampling

A
  • easy to carry out
  • inexpensive
25
Q

disadvantages of opportunity sampling

A
  • unlikely to provide a representative sample
  • highly dependednt of an individual researcher
26
Q

what is a discrete variable

A
  • can take only specific values
27
Q

LDS: what is the warmest place in the UK

A

heathrow

28
Q

LDS: what are the driest places in the UK

A
  • heathrow
  • hurn
29
Q

LDS: what are the order of places in the UK from the north to south

A
  1. Leuchars
  2. leeming
  3. heathrow
  4. hurn
  5. camborne
30
Q

LDS: what is the wettest coldest and windiest place in the UK

A

Leuchars

31
Q

LDS: why are there loads of missing values in 1987

A

there was a great storm in the UK in 1987

32
Q

LDS: what was the windiest month in the UK

A

may 2015

33
Q

LDS: rainfall of Perth

A
  • 0 OR
  • very high
34
Q

LDS: describe features of jacksonville

A
  • hot and humid
  • hurricanes (octobers of
35
Q

LDS: features of Beijing

A
  • inland
  • less wind
36
Q

LDS: what does tr mean

A

trace data = 0 to 0.05mm

37
Q

LDS: how to you clean data

A
  • delete n/a
  • removing anomalies
  • converting thr tr values to 0
38
Q

LDS: example of a qualitative piece of data

A

daily mean wind speed - beaufort scale
- fresh, light, moderate & strong

39
Q

LDS: example of a discrete variable

A

cloud coverage
- 0 to 8 oktas

40
Q

what is an outlier

A

unusual data

41
Q

what is an anomaly

A

error

42
Q

LDS: what is daily mean temp measured in

A

degrees C

43
Q

LDS: what is daily total rainfall measured in

A

mm

44
Q

LDS: what is daily mean windspeed measured in

A

beaufort scale

45
Q

LDS: what is wind gust measured in

A

knots
- 1kn =1.15 mph

46
Q

LDS: what is wind direction

A

bearing

47
Q

LDS: what is daily max rel. humidity measured in

A

%
- fog is when >95%

48
Q

LDS: what is daily mean total cloud measured in

A

oktahs (eights)
- 0 to 8

49
Q

LDS: what is daily mean pressure

A

1hPA = 100Pa

50
Q

LDS: what is daily mean visibility measured in

A

Dm
- decametres

Maths (16 decks)

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