chapter one - year one

Question 1

what is a census

Answer 1

observes or measures every member of a population

Question 2

what is an advantage of a census

Answer 2

it should give a completely accurate result

Question 3

what are the disadvantages of a census

Answer 3

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

Question 4

what is a sample

Answer 4

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

Question 5

what are the advantages of a sample

Answer 5

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

Question 6

what are disadvantages of a sample

Answer 6

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 7

what is simple random sampling

Answer 7

what every sample of size n had an equal chance of being selected

Question 8

what are advantages of simple random sampling

Answer 8

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 9

what are disadvantages of simple random sampling

Answer 9

not suitable when the population size or the sample size is large
a sampling frame is needed

Question 10

what is systematic sampling

Answer 10

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

Question 11

what are advantages of systematic sampling

Answer 11

simple and quick to use

Question 12

what are disadvantages of systematic sampling

Answer 12

a sampling frame is needed
it can introduce bias if the sampling frame is not random

Question 13

what is stratified sampling

Answer 13

the population is divided into mutually exclusive strata and a random sample is taken from each
no. in stratum/no. in population x overall sample size

Question 14

what are advantages of stratified sampling

Answer 14

sample accurately reflects the population structure
guarantees proportional representation of groups within a population

Question 15

what are disadvantages of stratified sampling

Answer 15

population must be clearly classified into distinct strata
selection within each stratum suffers from the same disadvantages as simple random sampling: sampling frame needed and not suitable when the population size or the sample size is large

Question 16

what is quota sampling

Answer 16

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

Question 17

what are advantages of quota sampling

Answer 17

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

Question 18

what are disadvantages of quota sampling

Answer 18

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 19

what is opportunity sampling ( convenience sampling )

Answer 19

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 20

what are advantages of opportunity sampling

Answer 20

easy to carry out
inexpensive

Question 21

what are disadvantages of opportunity sampling

Answer 21

unlikely to provide a representative sample
highly dependent on individual researcher