Chapter 1 - Data Collection

Question 1

Methods of Random Sampling

Answer 1

Simple Random, Systematic & Stratified

Question 2

Simple Random Sample

Answer 2

Everyone has an equal chance of being chosen

Question 3

Advantages of a Simple Random Sample

Answer 3

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

Question 4

Disadvantages of a Simple Random Sample

Answer 4

Not suitable when the population size or the sample size is large as it is time consuming, disruptive and expensive, sampling frame needed

Question 5

How to carry out a Simple Random Sample

Answer 5

Using your sampling frame, number all the elements and use random number generator to generate x different numbers.

Question 6

Systematic Sampling

Answer 6

Required elements chosen at regular intervals

Question 7

Advantages of Systematic Sampling

Answer 7

Simple and quick to use, suitable for large samples and large populations, every member has the same probability of being chosen.

Question 8

Disadvantages of Systematic Sampling

Answer 8

Sampling frame needed, can introduce bias if sampling frame is not random.

Question 9

How to carry out a systematic sample

Answer 9

Take every Kth element where K= Population Size / Sample Size. Choose starting point between 1 and K using a simple random sample.

Question 10

Stratified Sampling

Answer 10

Population divided into mutually exclusive strata

Question 11

Advantages of Stratified Sampling

Answer 11

Accurately reflects population structure, Guarantees proportional representation of groups within population.

Question 12

Disadvantages of Stratified Sampling

Answer 12

Population must be clearly classified into distinct strata, Selection within each stratum suffers from same disadvantages as simple random sampling

Question 13

How to carry out a stratified sample

Answer 13

Population divided into groups (strata) and a simple random sample carried out in each group. Same proportion, sample size / population size, used when sample is large and population naturally divides into groups.

Question 14

Methods of Non-random Sampling

Answer 14

Quota & Opportunity

Question 15

Quota Sampling

Answer 15

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

Question 16

Advantages of Quota Sampling

Answer 16

Allows small sample size to still be representative of the population, no sampling frame required, quick, easy, inexpensive, allows for easy comparison between different groups within a population.

Question 17

Disadvantages of Quota Sampling

Answer 17

Non-random sampling can introduce bias, population must be divided into groups which can be costly and inaccurate, increasing scope of study increases number of groups which adds time and expense, non-response are not recorded,

Question 18

How to carry out a Quota Sample

Answer 18

Population divided into groups according to characteristic. A quota of items / people in each group is set to try and reflect the group’s proportion in the whole population. Interviewers selects the actual sampling units.

Question 19

Opportunity Sampling

Answer 19

Taking a sample from people who are available at the time of study is carried out and who fit the criteria you are looking for.

Question 20

Advantages of Opportunity Sampling

Answer 20

Easy to carry out, inexpensive.

Question 21

Disadvantages of Opportunity Sampling

Answer 21

Unlikely to provide a representative sample, highly dependent on individual researcher.

Question 22

Quantitative Data

Answer 22

Variables or data associated with numerical observations

Question 23

Qualitative Data

Answer 23

Variables or data associated with non-numerical observations

Question 24

Continuous Data

Answer 24

Can take any value in a given range

Question 25

Discrete Data

Answer 25

Can only take specific values

Question 26

Sampling Unit

Answer 26

Individuals units/items of a population

Question 27

Census

Answer 27

Observes or measures every member of a population

Question 28

Advantages of a Census

Answer 28

Should give completely accurate result

Question 29

Disadvantages of a Census

Answer 29

Time consuming and expensive, cannot be used when the testing process destroys the item, hard to process large quantity of data

Question 30

Sample

Answer 30

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 31

Advantages of a Sample

Answer 31

Less time consuming and expensive than a census, fewer people have to respond, less data to process than in a census.

Question 32

Disadvantages of a Sample

Answer 32

The data may not be as accurate, the sample may not be large enough to give information about small sub-groups of the population.