Sampling

Question 1

What is a Census?

Answer 1

measures every member of a population

Question 2

What is a Sample?

Answer 2

Observations are taken from a subset of a population

Question 3

What are the advantages and disadvantages of using a Census?

Answer 3

+ results completely accurate

• time consuming and expensive
• difficult to process large sets of data

Question 4

What are the advantages and disadvantages of using a Sample?

Answer 4

+ less time consuming than a Census
+Fewer people have to respond
+less data needs to be processed
- wont be as accurate
- might not be big enough to give information on other subsets of population

Question 5

Simple Random Sampling: ADVANTAGES

Answer 5

+ free of bias
+ easy and cheap for small samples
+ each sampling unit has equal chance of selection

Question 6

Simple Random Sampling: DISADVANTAGES

Answer 6

• not suitable for large samples/ populations
• sampling frame is needed

Question 7

What is Systematic Sampling?

Answer 7

A method of random sampling where elements are chosen at regular intervals from an ordered list

Question 8

Systematic Sampling: ADVANTAGES

Answer 8

+ simple and quick to use
+ suitable for large samples/ populations

Question 9

Systematic Sampling: DISADVANTAGES

Answer 9

• sampling frame is needed
• bias introduced if sampling frame is not random

Question 10

What is Stratified Sampling?

Answer 10

A method of random sampling where the population is divided into mutually exclusive subsets and a random sample is take from each

Question 11

Stratified Sampling: ADVANTAGES

Answer 11

+ sample accurately reflects population structure
+ proportional representation of groups within a population

Question 12

Stratified Sampling: DISADVANTAGES

Answer 12

• population must be clearly classified into distinct subsets
  -same disadvantages of simple random sampling within each subset

Question 13

How do you work out how many are sampled in each subset for Stratified Sampling ?

Answer 13

(number in subset/ number in population) * sample size

Question 14

What is Quota Sampling?

Answer 14

A method of non-random sampling in which a researcher takes a sample that reflects characteristics of the whole population.

Question 15

Quota Sampling: ADVANTAGES

Answer 15

+ small sample be representative of population
+no sapling frame needed
+ quick, easy and inexpensive
+ easy comparison between different groups within a population

Question 16

Quota Sampling: DISADVANTAGES

Answer 16

• can introduce bias
• dividing into subgroups can be costly or inaccurate
• non-responses are not recorded

Question 17

What is Opportunity/ Convenience Sampling?

Answer 17

Non- random sampling method. Sample is taken from people available at the time or who fit the criteria of the study

Question 18

Opportunity/Convenience Sampling: ADVANTAGES

Answer 18

+ easy and inexpensive

Question 19

Opportunity/Convenience Sampling: DISADVANTAGES

Answer 19

• unlikely to provide representative result
• highly dependent on individual researcher

Question 20

What is a Sampling Frame?

Answer 20

A sampling frame is the set of individuals or items from which a sample has been drawn.