statistics Y1

Question 1

Population

Answer 1

the whole set of items that are of interest

Question 2

Census

Answer 2

observes or measures every member of a population

Question 3

Sample

Answer 3

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

Question 4

Advantages and disadvantages of a census

Answer 4

Advantages:
- gives a completely accurate result
Disadvantages:
- time consuming and expensive
- cannot be used when testing process destroys the item
- hard to process (as a large sample)

Question 5

Advantages and disadvantages of using a sample

Answer 5

Advantages:
- less time consuming and expensive
- fewer people have to respond
- less data to process
Disadvantages:
- data may not be as accurate
- sample may not be large enough to give information about subgroups

Question 6

Sampling units

Answer 6

Individual units of a population

Question 7

Sampling frame

Answer 7

The list of sampling units named or numbered individually

Question 8

Random sampling advantages

Answer 8

Every sample has an equal chance of being selected, meaning it is representative and removes bias

Question 9

3 methods of random sampling

Answer 9

• simple random sampling
• systematic sampling
• stratified sampling

Question 10

Simple random sampling

Answer 10

• need a sampling frame
• either generate random numbers corresponding to sampling frame or lottery sampling
• every sample has an equal chance of being selected

Question 11

Systematic sampling

Answer 11

• required elements are chosen at regular intervals from an ordered list
  e.g. if a sample of size 20 was needed from a population of 100, you would take every fifth person, starting at a random number from 1 to 5

Question 12

Stratified sampling

Answer 12

The population is divided into mutually exclusive strata (e.g. male and female)
and a random sample is takes for each

number sampled in a stratum =
number in stratum/number of population * overall sample size

Question 13

Adv and disadv of simple random sampling

Answer 13

adv:
-free of bias
-cheap and easy to implement for small populations and samples
- each sampling unit has a known and equal chance of selection
disadv:
- not suitable when population size or sample size is large as potentially time consuming, disruptive and expensive

Question 14

Adv and disadv of systematic sampling

Answer 14

adv:
- simple and quick to use
- suitable for large samples and large populations
Disadv:
- sampling frame is needed
- can introduce bias if sampling frame is not random

Question 15

Adv and disadv of stratified sampling

Answer 15

adv:
- sample accurately reflects the population structure
- guarantees proportional representation of groups within a population
Disadv:
- population must be clearly classified into distinct strata
- selection within each stratum suffers from the same disadvantages as simple random sampling

Question 16

Two types of non-random sampling

Answer 16

• quota sampling
• opportunity sampling

Question 17

Quota sampling

Answer 17

an interviewer or researcher selects a sample that reflects the characteristics of the whole population
- the population is divided into groups according to a given characteristic. The size of each group determines the proportion of the sample that should have the characteristic
- an interviewer would meet people, assess their group and allocate them to the appropriate quota
- continues until all the quotas have been filled

Question 18

Opportunity sampling

Answer 18

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

Question 19

Quota sampling adv and disadv

Answer 19

Adv:
- allows small sample to still be representative of population
- no sampling frame requires
- quick, easy, cheap
- allows for easy comparison between different groups
Disadv:
- can introduce bias
- division into groups can be costly or inaccurate
- increasing scope of study increases number of groups, increasing time and expense
- non-responses are not recorded as such

Question 20

Opportunity sampling adv and disadv

Answer 20

Adv:
- easy to carry out
- inexpensive
Disadv:
- unlikely to produce a representative sample
- highly dependent on individual researcher

Question 21

Discrete variable

Answer 21

A variable that can only take specific values in a given range (e.g. you cannot have 2.3 children)

Question 22

Continuous variable

Answer 22

A variable that can take any value in a given range