sampling

Question 1

population

Answer 1

group that we want to find information about
-the whole set of items that are of interest

Question 2

a census

Answer 2

observes or measures every member of a population.

Question 3

a 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

A sampling unit

Answer 4

a person/object to be sampled

Question 5

sampling frame

Answer 5

collection of all the sampling units

Question 6

census advantage

Answer 6

It should give a completely accurate result

Question 7

census disadvantage

Answer 7

Time time-consuming and expensive
* Cannot be used when the testing
process destroys the item
* Hard to process large quantities of data

Question 8

sample advantage

Answer 8

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

Question 9

sample disadvantage

Answer 9

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

Question 10

random sampling

Answer 10

every member of the population has an equal chance of being selected.

Question 11

advantage of random sampling

Answer 11

-representative of the population
- Random sampling also helps to remove bias from a sample.

Question 12

there are three methods of random sampling

Answer 12

-Simple random sampling
* Systematic sampling
* Stratified sampling

Question 13

simple random sampling

Answer 13

A simple random sample of size n is one where every sample of size n has an equal chance of being selected.

Question 14

to carry out random sampling you need

Answer 14

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.
-e.g generating random numbers using a calculator, or computer ..
-lottery sampling (sampling frames written on tickets in a hat)

Question 15

systematic sampling

Answer 15

the required elements are chosen at regular intervals from an ordered list.
for example, every 10th member of the sample frame could be selected.

Question 16

In stratified sampling, the population is divided into

Answer 16

mutually exclusive strata (males and
females, for example) and a random sample is taken from each.

Question 17

formula used

Answer 17

The number sampled in a stratum = number in stratum /number in population
× Overall sample size

Question 18

simple random sampling advantages

Answer 18

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

Question 19

simple random sampling disadvantages

Answer 19

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

Question 20

systematic sampling advantages

Answer 20

Simple and quick to use
* Suitable for large samples and large
populations

Question 21

disadvantages in systematic sampling

Answer 21

A sampling frame is needed
* It can introduce bias if the sampling frame is
not random

Question 22

stratified sampling advantages

Answer 22

The sample accurately reflects the population
structure
* Guarantees proportional representation of
groups within a population

Question 23

stratified sampling disadvantages

Answer 23

The population must be clearly classified into
distinct strata
* Selection within each stratum suffers from
the same disadvantages as simple random
sampling

Question 24

examples of non-random sampling

Answer 24

-quote sampling
-opportunity sampling

Question 25

quota sampling

Answer 25

In quota sampling, an interviewer or researcher selects a sample that reflects the characteristics of the whole population.

Question 26

opportunity sampling/convenience sampling

Answer 26

Opportunity sampling consists of taking the sample from people who are available at the time the study is carried out and who fits the criteria you are looking for.

Question 27

quota sampling advantages

Answer 27

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 28

quota sampling disadvantages

Answer 28

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 29

opportunity sampling advantages

Answer 29

-Easy to carry out
* Inexpensive

Question 30

opportunity sampling disadvantages

Answer 30

Unlikely to provide a representative sample
* Highly dependent on individual researcher