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Maths > Chapter 1 Stats 1 > Flashcards

Chapter 1 Stats 1 Flashcards

1
Q

Census

A
  • observes or measures every member of a population

Adv:
- completely accurate

Dis:

  • time consuming, expensive
  • cannot be used when the testing destroys the item
  • hard to process large quantity of data
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2
Q

Sample

A
  • a sample is a selection of observations taken from a subset of the population which is used to find out information about the population as a whole

Adv:

  • less time-consuming and expensive
  • Few people have to respond
  • less data to process than the census

Dis:

  • not as accurate
  • The sample may not be large enough to give information about small subgroups of the population
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3
Q

What are sampling units

A

Individual units of a population

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4
Q

What is a sampling frame

A

List of sampling units, with each unit given an identifying name or number

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5
Q

Simple random sampling

A
  • a unique number is given to the sampling frame and a random number generator is used to get them
    Adv:
  • free of bias
  • easy and cheap to implement for small populations and samples
  • each sampling unit has a known and equal chance of selection
    Dis:
  • SF is needed
  • not suitable for large population
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6
Q

Systematic sample

A
  • required elements are chosen at regular intervals from an ordered list
    Adv:
  • simple, quick, suitable for large samples and populations

Dis:
- sampling frame is needed, can introduce bias if sampling frame is not random

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7
Q

Stratified sampling

A
  • The population is divided into mutually exclusive strata and random samples taken from each

Adv:

  • sample accurately reflects the population structure
  • guarantees proportional representation of a group within a population

Dis:

  • population must be clearly classified into distinct strata
  • selection within each strata suffers from the same disadvantages of simple random sample
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8
Q

Quota sampling

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

Adv:

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

Dis:

  • bias, population must be divided into groups which can be costly or inaccurate
  • non-responses are not recorded
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9
Q

Opportunity sampling

A
  • consists of taking the samples from people who are available at the time the study is carried out and who fit the criteria you’re looking for

Adv:
- easy and inexpensive

Dis:

  • Unlikely to provide a representative sample
  • highly dependent on individual researcher
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10
Q

Types of data

A

Quantitative - numerical
Continuous, (time) discrete (no. Of people)

Qualitative - non-numerical

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11
Q

5 weather stations in UK

A
  • leuchars
  • Leeming
  • Heathrow
  • Hurn
  • Camborne
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12
Q

3 weather stations in the world

A

Jacksonville (near Florida)

Bejijng (east China)

Perth (west Australia)

  • the only data recorded is: temp, rainfall, pressure, windspeed
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13
Q

what is meant by a population

A

Collection of individual items

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14
Q

The large data set: daily total rainfall

A
  • amounts less than 0.05 are recorded as ‘tr’ or ‘trace’

- includes snow and hail

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15
Q

The large data set: daily maximum relative humidity

A

relative humidities above 95% give rise to misty and foggy conditions

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16
Q

The large data set: Beaufort scale

A

a scale which measures wind speed

  • 0 - calm - less than 1 knot
  • 1-3 - light - 1 to 10 knots
  • 4 - moderate - 11 to 16 knots
  • 5 - fresh - 17 to 21 knots
17
Q

The large data set: daily total sunshine

A

recorded to the nearest tenth of an hour

18
Q

The large data set: daily mean wind direction and windspeed

A
  • averaged over 24 hours from midnight to midnight

- mean wind direction is given as a bearing and as cardinal (compass) directions

19
Q

The large data set: daily mean cloud cover

A
  • measured in ‘oktas’ or eighths of the sky covered by cloud
20
Q

The large data set: daily mean visibility

A
  • measured in decametres (Dm)

- is the greatest horizontal distance at which an object can be seen in daylight

21
Q

The large data set: daily mean pressure

A
  • measured in hectopascals hPa
22
Q

The large data set: what is measured for the uk locations

A
  • temperature
  • rainfall
  • sunshine
  • wind direction and speed
  • gust
  • humidity
  • cloud cover
  • visibility
  • pressure
23
Q

explain systematic sampling

A
  • label members or obtain an ordered list
  • divide number of members by how many samples are needed
  • select first person using random numbers
  • select every other person from the list at regular intervals
24
Q

explain stratified sampling

A
  • give the different members of the group a number

- use random numbers to select the right number of people from each group

25
Q

define population

A

A complete collection of individual units e.g. people or items

26
Q

when was the large data set recorded

A

may - October

  • 2015
  • 1987

Maths (2 decks)

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