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statistics > UNIT 1: The collection of data > Flashcards

UNIT 1: The collection of data Flashcards

1
Q

Primary Data

A

Primary data is collected by, or for, the person who is going to use it.

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2
Q

Secondary Data

A

Secondary data has been collected by someone else

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3
Q

Advantages Primary Data

A
  • Accuracy is known
  • Collection is known
  • Can find answers to specific questions
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4
Q

Disadvantages Primary Data

A
  • Time consuming

- Can be expensive

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5
Q

Advantages Secondary Data

A
  • Cheap
  • Quick
  • Can be reliable from Office of National Statistics, or sporting results pages
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6
Q

Disadvantages Secondary Data

A
  • Don’t know method of collection
  • May not be able to find answers to specific questions
  • Websites may be unreliable
  • May be out of date
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7
Q

Qualitative Data

A

Non numerical observation

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8
Q

Quantitative Data

A

Numerical observation

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9
Q

Continuous Data

A

Can take any numerical value on a scale

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10
Q

Discrete Data

A

Can only take particular values (eg. Shoe size, number of words typed per minute)

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11
Q

Ordinal Data

A

Data from a numerical rating scale

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12
Q

Categorical Data

A

Data which can be sorted into non overlapping categories/class intervals

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13
Q

Bivariate Data

A

Data which involves pairs of related data (each pair of data points refer to one item)

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14
Q

Multivariate Data

A

Data which involves three or more related data values. Each set of data values refers to one item

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15
Q

Population

A

Everything or everybody that could possibly be involved in an investigation

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16
Q

Census

A

A survey or investigation with data taken from every member of the population

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17
Q

Sample

A

Contains information about part of the population

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18
Q

Census: Advantages

A
  • Accurate

- Takes the whole population into account

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19
Q

Census:

Disadvantages

A
  • Time consuming
  • Expensive
  • Difficult to ensure the whole population is used
  • Lots of data to handle
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20
Q

Sample: Advantages

A
  • Cheaper than a census
  • Quicker than a census
  • Less data to handle
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21
Q

Sample: Disadvantages

A

-Not completely representative

22
Q

Bias

A
  • If a sample is not representative of the population it is biased.
  • It could be selected unfairly.
  • It could be that the sample size is too small
23
Q

Sampling Frame

A

A LIST OF all the people/things that we are selecting our sample from

24
Q

Sampling Unit

A

The people/things that are being sampled

25
Q

Electoral Roll

A

A list of people who are eligible to vote in the UK. The easiest way to get a list of adults in a geographical area

26
Q

Petersen Capture-Recapture Formula

A

M/N=m/n

M=total tagged at start
N=population (unknown)
m=number tagged in sample
n=sample size

27
Q

Petersen Capture-Recapture Assumptions

A
  • Population is closed (state specifics in context)
  • Tagging doesn’t affect survival rate
  • Tags don’t get lost/removed and are easily recognisable
  • The sample size is large enough to represent the population.
  • The probability of being caught is equal for all individuals in the population
28
Q

Random Sampling

A

In a random sample every member of the population has equal chance of being selected

29
Q

Random Sampling Advantages

A
  • Provided it is large the sample is likely to be representative of the population.
  • Choice of members of sample is unbiased
30
Q

Random Sampling Disadvantages

A
  • Needs a full list of the whole population

- Needs a large sample

31
Q

Methods of random sampling

A

Always number your sampling frame

(1) Pull numbers from hat
(2) Use RanInt function on your calculator
(3) Use a random number table: select starting point on table randomly

32
Q

Opportunity Sampling

A

Use the people or things that are available at the time

33
Q

Quota Sampling

A

Group population by characteristics (eg gender/age) and then ask a specific number from each quota

34
Q

Judgement sampling

A

Use your judgement to select a sample that you think is representative

35
Q

Cluster Sampling

A

Population forms in natural groups. Your sampling frame is the list of clusters, random select clusters to sample

36
Q

Systematic Sampling

A

Pick a random starting point and then select every eg 10th item on your sampling frame. Need to number sampling frame

37
Q

What four things to comment on when non random sampling

A
  • Bias
  • Cost
  • Time
  • Sample size
38
Q

Stratified sampling calculation

A

(Total in stratum / Total population) × sample size

39
Q

Pilot Survey - reasons

A
  • To check the response rate
  • To check the questions make sense
  • To check you collect the data you are expecting
40
Q

Questionnaire key points

A
  • Open questions - free written answers
  • Closed questions - multi choice or opinion scale (Must include “other” or “don’t know”)
  • Always include a timeframe (eg: yesterday, last week, last year etc)
  • Avoid questions where respondents would be tempted to lie.
  • Don’t ask leading questions like “Don’t you agree….?”
41
Q

Interview: Advantages

A
  • High response rate
  • Can explain the questions
  • Can explain their answers
  • Can put people at ease
42
Q

Interview: Disadvantages

A
  • Less honest for personal questions/trying to impress the interviewer
  • Time-consuming, therefore expensive
  • Bias in who the interviewer speaks to
  • Sample size is small
43
Q

Anonymous Questionnaire: Advantages

A
  • Honest for personal questions
  • Quick, cheap
  • No interviewer bias
  • Sample size can be a large as you like
44
Q

Anonymous Questionnaire: Disadvantages

A
  • Low response rate
  • May not understand the questions
  • May not understand the answers
45
Q

Reliable data

A

Data which can be replicated

46
Q

Valid data

A

Data which measures what you want it to measure

47
Q

Cleaning Data

A

The process of identifying gaps, anomalies or errors in the data. Usually done on Excel with “sort” and “find” function

48
Q

Extraneous variables

A

A variable you are not interested in that could affect your result

49
Q

Control group

A

Select two groups randomly. Give the control group no treatment. Give the test group treatment. Compare the results. (Often used for medical trials)

50
Q

Matched pairs

A

Two groups where each individual in one group is paired with an individual in the second group. They should have everything in common except the factor being studied.

51
Q

Hypothesis

A

An idea that can be tested by collecting and analysing data.

statistics (10 decks)

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