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Maths Edexcel A Level > AS Statistics > Flashcards

Flashcards in AS Statistics Deck (73)
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1

Population

The whole set of items that are of interest

2

Census

Observes or measures every member of a population

3

Sample

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

4

Sampling frame

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

5

Advantages/disadvantages of a census

Advantages:
Completely accurate result
Disadvantages:
Time consuming, expensive, cannot be used when testing process destroys the item, hard to process large quantity of data

6

Sample advantages/ disadvantages

Advantages:
Less time consuming/expensive, fewer people have to respond, less data to process than in a census
Disadvantages:
Data may not be as accurate, sample may not be large enough to give data about small subgroups of the population

7

Sampling units

Individual units of a population

8

Simple random sample

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

9

Systematic sampling

Required elements are chosen at regular intervals from an ordered list

10

Stratified sampling

Population is divided into mutually exclusive strata and a random sample is taken from each

11

Simple random sampling advantages/disadvantages

Advantages: free of bias, easy and cheap to implement for small samples/populations, each sampling unit has a known and equal chance of selection
Disadvantages: not suitable for large populations (time consuming, disruptive, expensive), a sampling frame is needed

12

Systematic sampling advantages/disadvantages

Advantages: simple and quick to use, suitable for large samples/populations
Disadvantages: a sampling frame is needed, can introduce bias if the sampling frame is not random

13

Stratified sampling advantages/disadvantages

Advantages: sample accurately reflects population structure, guarantees proportional representation of groups within a population.
Disadvantages: population must be classified into distinct strata, selection within each stratum suffers from same disadvantages as simple random sampling

14

Quota sampling

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

15

Opportunity sampling

Consists 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

16

Quota sampling advantages/disadvantages

Advantages: allows a small sample to still be representative of the whole population, no sampling frame required, quick, easy and inexpensive, allows for easy comparison between different groups within a population
Disadvantages: non-random sampling can introduce bias, population must be divided into groups which can be costly and inaccurate, increasing scope of study increases number of groups (adding time and expense), non-responses are not recorded as such

17

Opportunity sampling advantages/disadvantages

Advantages: easy to carry out, inexpensive
Disadvantages: unlikely to provide a representative sample, highly dependent on individual researcher

18

Quantitative data/variables

variables or data associated with numerical observations

19

Qualitative data/variables

variables or data associated with non-numerical observations

20

continuous variable

a variable that can take any value in a given range

21

discrete variable

a variable that can take only specific values in a given range

22

grouped frequency table (gft)

the specific data values are not shown but are included in groups (or classes)

23

mid-point (gft)

average of class boundaries

24

Daily mean temperature units

degrees Celsius

25

Daily total rainfall units

mm
(Amounts less than 0.05 mm are recorded as 'tr' or 'trace')

26

Daily total sunshine

recorded to the nearest tenth of an hour

27

Daily mean windspeed/daily maximum gust units

knots

28

Daily maximum relative humidity

Given as a percentage of air saturation with water vapour.
Above 95% gives rise to misty and foggy conditions

29

Daily mean cloud cover units

'okras' (eighths of the sky covered by cloud)

30

Daily mean visibility units

decametres (Dm)