Stats 1.1: Data Collection

Question 1

What is the definition of a population?

Answer 1

The whole set of items that are of interest

Question 2

What is the definition of a sample ?

Answer 2

Some subset of the population intended to represent the population

Question 3

What is a sampling unit ?

Answer 3

Each individual thing in the population that can be sampled

Question 4

What is a sample frame?

Answer 4

When sampling units of a population are individually named or numbers to form a list

Question 5

What is a census?

Answer 5

Data collected from the entire population

Question 6

What is the advantage of using a census?

Answer 6

Should give completely accurate representation so it is unbiased

Question 7

What are the disadvantages of a census?

Answer 7

Time consuming and expensive
Can not be used when testing involves destruction
Large volume of data to process
Can be difficult to make sure all members are surveyed

Question 8

What are the advantages of using a sample?

Answer 8

Cheaper
Quicker
Less data to process

Question 9

What are the disadvantages of using a sample?

Answer 9

Data may not accurately reflect the population, different samples could give different results
Data may not be large enough to represent small sub-groups

Question 10

What is simple random sampling ?

Answer 10

Every sample has an equal chance of being selected and each selection is independent of the others

Question 11

What do you carry out simple random sampling ?

Answer 11

In the sampling frame, each item has an identifying number. Use a random number generator to get the numbers

Question 12

What are the advantages is using simple random sampling ?

Answer 12

Bias free because each number has a known equal chance of being selected
Each and cheap to implement

Question 13

What are the disadvantages of using simple random sampling ?

Answer 13

Not suitable when population size is large as it can be difficult to track all members say if you are doing a nationwide sample
Sampling frame is needed

Question 14

How do you carry out systematic sampling ?

Answer 14

Required elements are chosen at regular intervals in ordered list

Question 15

What are the advantages of systematic sampling ?

Answer 15

Simple and quick to use
Suitable for larger samples/populations
Can be used for quality control in manufacture
Should give an unbiased sample

Question 16

What are the disadvantages of systematic sampling?

Answer 16

Sampling frame is needed as you must number each member of the population
Can introduce bias if sampling frame is not random I.e. if the interval coincides with a pattern in the population

Question 17

How is stratified sampling carried out ?

Answer 17

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

Question 18

When is stratified sampling used?

Answer 18

When sample is large and population naturally divides into groups

Question 19

What are the advantages of stratified sampling ?

Answer 19

Reflects population structure
Guarantees proportional representation of groups within population
Useful when results may vary depending on categories

Question 20

What are the disadvantages of stratified sampling ?

Answer 20

Population must be clearly classified into distinct strata
Selection within each stratum suffers from same disadvantages as simple random sampling
Extra detail needed can make it expensive

Question 21

What is cluster sampling ?

Answer 21

When the population can be divided into distinct groups and the clusters should be groups that you expect to give similar results.

Question 22

What are the 3 types of random sampling?

Answer 22

1 simple random
2 systematic
3 stratified

Question 23

What are the 2 types of non-random sampling?

Answer 23

1 Quota
2 Opportunity

Question 24

What is the general definition of quota sampling?

Answer 24

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

Question 25

How does quote sampling work?

Answer 25

1 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 that characteristic. 2 As an interviewer, you would meet people, assess their group and then, after interview, allocate them into the appropriate quota. 3 This continues until all quotas have been filled. If a person refuses to be interviewed or the quota into which they fit is full, then you simply ignore them and move on to the next person.

Question 26

What is another name for opportunity sampling?

Answer 26

Convenience sampling

Question 27

What is the general definition of opportunity sampling?

Answer 27

It 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.

Question 28

What are the advantages of quota sampling?

Answer 28

Allows a small sample to still be representative of the population No sampling frame required Quick, easy and inexpensive Allows for easy comparison between different groups within a population.

Question 29

What are the disadvantages of quote sampling?

Answer 29

Non-random sampling can introduce bias Population must be divided into groups, which can be costly or inaccurate Increasing scope of study increases number of groups, which adds time and expense Non-responses are not recorded as such

Question 30

What are the advantages of opportunity sampling?

Answer 30

Easy to carry out Inexpensive

Question 31

What are the disadvantages of opportunity sampling?

Answer 31

Unlikely to provide a representative sample Highly dependent on individual researcher

Question 32

What is quantitative data?

Answer 32

Variables or data associated with numerical observations

Question 33

What is qualitative data?

Answer 33

Variables or data associated with non-numerical observations

Question 34

What is a continuous variable?

Answer 34

A variable that can take any value in a given range

Question 35

What is a discrete variable?

Answer 35

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