Data Collection

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 the population

Question 3

Sample

Answer 3

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

Question 4

Advantages of a census

Answer 4

Should give a completely accurate result

Question 5

Disadvantages of a census

Answer 5

Time-consuming and expensive
Cannot be used when the testing process destroys the item
How to process large quantity of data

Question 6

Advantages of a sample

Answer 6

Less time-consuming and expensive than a census
Fewer people have to respond
Less data to process than in a census

Question 7

Disadvantages of a sample

Answer 7

The data may not be as accurate

The sample may not be large enough to give information about small subgroups of the population

Question 8

Sampling units

Answer 8

Individual units of a population

Question 9

Sampling frame

Answer 9

A list formed from sampling units of a population which are individually named or numbered

Question 10

Simple random sample

Answer 10

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

Question 11

How do you carry out a simple random sample

Answer 11

You need a sampling frame, usually a list of people or things. Each person or thing is allocated a unique number and a selection of these numbers is chosen at random

Two methods: generating random numbers, lottery sampling

Question 12

Systematic sampling

Answer 12

The required elements are chosen at regular intervals from an ordered list

The first person to be chosen should be chosen at random

Question 13

Stratified sampling

Answer 13

The population is divided into mutually exclusive strata (Males and females, for example) and a random sample is taken from each

The proportion of each strata samples should be the same.

Question 14

Formula to calculate the number of people that should be sampled from each stratum

Answer 14

The number sampled in a stratum= (number in stratum/number in population) x overall sample size

Question 15

Advantages of simple random sampling

Answer 15

Free of bias
Easy and cheap to implement for small populations and small samples
Each sampling unit has a known an equal chance of selection

Question 16

Disadvantages of simple random sampling

Answer 16

Not suitable when the population size or the sample size is large
A sampling frame is needed

Question 17

Advantages of systematic sampling

Answer 17

Simple and quick to use

Suitable for large samples and large populations

Question 18

Disadvantages of systematic sampling

Answer 18

A sampling frame is needed

It can introduce bias if the sampling frame is not random

Question 19

Advantages of stratified sampling

Answer 19

Sample accurately reflects the population structure

Guarantees proportional representation of groups within the population

Question 20

Disadvantages of stratified sampling

Answer 20

Population must be clearly classified into distinct strata

Selection within each stratum suffers from the same disadvantages are simple random sampling

Question 21

Quota sampling

Answer 21

An interview or research a select 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 that characteristic

Question 22

Opportunity sampling/Convenience sampling

Answer 22

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 23

Advantages of quota sampling

Answer 23

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 24

Disadvantages of quota sampling

Answer 24

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

Question 25

Advantages of opportunity sampling

Answer 25

Easy to carry out

Inexpensive

Question 26

Disadvantages of opportunity sampling

Answer 26

Unlikely to provide a representative sample

Highly dependent on individual researcher

Question 27

Quantitative variables/data

Answer 27

Variables or data associated with numerical observations

Question 28

Qualitative variables/data

Answer 28

Variables or data associated with non-numerical observations

Question 29

Continuous variable

Answer 29

Variables that can take any value in a given range

Question 30

Discrete variable

Answer 30

Variables that can take only specific values in a given range