AS Statistics

Question 1

Population

Answer 1

The whole set of items that are of interest

Question 2

Sample

Answer 2

Subset of the population intended to represent the population

Question 3

Sampling Unit

Answer 3

Each individual thing in the population that can be sampled

Question 4

Sampling Frame

Answer 4

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

Question 5

Census

Answer 5

Data collected from the entire population

Question 6

Advantages of a Census

Answer 6

• should give a completely accurate result

Question 7

Measures of Central Tendancy

Answer 7

Values to do with the centre of data e.g. mean, median and mode

Question 8

Comparing Box Plots

Answer 8

• IQR + context
• Median + context (“on average”)

Question 9

Comparing Data

Answer 9

• a measure of location
• a measure of spread

Question 10

Bivariate Data

Answer 10

Data which has pairs of values for two variables

Question 11

Casual Relationship

Answer 11

Two variables have a casual relationship if a change in one variable causes a change in the other

Question 12

Interpolation

Answer 12

Making a prediction based on a value inside the range of given data

Question 13

Extrapolation

Answer 13

Making a prediction based on a value outside the range of given data

Question 14

Systematic Sampling

Answer 14

Required elements are chosen at regular intervals in an ordered list

Question 15

Stratified Sampling

Answer 15

Population divided into groups (strata) and a simple random sample carried out in each group

Question 16

Quota Sampling

Answer 16

Divide population into groups then determine the size of each group in the sample to reflect proportions within the population. Actively choose people within each group until the quota of each group is filled

Question 17

Opportunity Sampling

Answer 17

Find people at the same time the survey is being carried out

Question 18

Random Sampling

Answer 18

Each thing in the sampling frame has an equal chance of being chosen, in order to avoid bias

Question 19

Advantages of a Census (1)

Answer 19

• should give a completely accurate result

Question 20

Disadvantages of a Census (4)

Answer 20

• time consuming
• expensive
• large volume of data to process
• can’t be used when testing involves destruction

Question 21

Advantages of a Sample (3)

Answer 21

• quicker
• cheaper
• less data to process

Question 22

Disadvantages of a Sample (2)

Answer 22

• may not be representative
• possible bias

Question 23

Advantages of Random Sampling (2)

Answer 23

• bias free
• easy and cheap to implement

Question 24

Disadvantages of Random Sampling (3)

Answer 24

• not suitable when population size is large
• sampling frame needed
• may not be representative

Question 25

Advantages of Systematic Sampling (3)

Answer 25

- simple and quick to use - suitable for large samples/populations - no bias

Question 26

Disadvantages of Systematic Sampling (2)

Answer 26

- sampling frame needed - bias can be introduced if sampling frame not random

Question 27

Advantages of Stratified Sampling (2)

Answer 27

- reflects population structure - guarantees proportional representation of groups within population

Question 28

Disadvantages of Stratified Sampling (2)

Answer 28

- population must be clearly classified into distinct strata - selection within each stratum suffers from same disadvantages as random sampling

Question 29

Advantages of Quota Sampling (4)

Answer 29

- allows small sample to be representative - no sampling frame needed - quick, easy and inexpensive - allows for easy comparison between different groups

Question 30

Disadvantages of Quota Sampling (2)

Answer 30

- can introduce bias - population must be divided into groups

Question 31

Advantages of Opportunity Sampling (2)

Answer 31

- easy to carry out - inexpensive

Question 32

Disadvantages of Opportunity Sampling (2)

Answer 32

- unlikely to provide a representative sample - highly dependent on individual researcher