S1 - data collection

Question 1

population

Answer 1

the whole set of items that are of interest

Question 2

sample

Answer 2

some subset of the population intended to represent the population

Question 3

sampling unit

Answer 3

an individual thing in the population that can be sampled

Question 4

sampling frame

Answer 4

list of sampling units individually named or numbered

Question 5

census

Answer 5

data collected from the entire population

Question 6

advantages of a sample

Answer 6

cheaper
quicker
less data to process

Question 6

disadvantages of a sample

Answer 6

data may not be accurate
data may not be large enough to represent small sub-groups

Question 7

advantages of a census

Answer 7

should give completely accurate results

Question 8

disadvantages of a census

Answer 8

time consuming and expensive
cannot be used when testing involves destruction
large volume of data to process

Question 8

method for simple random sampling

Answer 8

in sampling frame each item has identifying number. use random number generator or lottery sampling

Question 8

simple random sampling

Answer 8

every sample has an equal chance of being selected

Question 9

advantages of simple random sampling

Answer 9

bias free
easy and cheap to implement
each number has a known equal chance of being selected

Question 10

disadvantages of simple random sampling

Answer 10

not suitable when population size is large
sampling frame needed

Question 11

systematic sampling

Answer 11

required elements are chosen at regular intervals in ordered list

Question 12

how to carry out systematic sampling

Answer 12

take every kth element where: k = pop size (N) / samp size (n)
starting at random item between 1 and k

Question 13

advantages of systematic sampling

Answer 13

simple and quick to use
suitable for large samples / populations

Question 14

disadvantages of systematic sampling

Answer 14

sampling frame needed
can introduce bias if sampling frame not random

Question 15

stratified sampling

Answer 15

population divided into groups (strata) and a simple random sample carried out in each group
used when sample is large and population naturally divides into groups

Question 16

how to carry out stratified sampling

Answer 16

same proportion samp size (n) / pop size (N) sampled from each strata

Question 17

advantages of stratified sampling

Answer 17

reflects population structure
guarantees proportional representation of groups within population

Question 18

stratified sampling disadvantages

Answer 18

population must be clearly classified into distinct strata
selection within each stratum suffers from same disadvantages as simple random sampling

Question 19

random sampling methods

Answer 19

simple
systematic
stratified

Question 20

non-random sampling

Answer 20

quota
opportunity/convenience

Question 21

quota sampling

Answer 21

population divided into groups according to characteristics, a quota of items in each group is set to try and reflect the group’s proportion in the whole population. interviewer selects the actual sampling units

Question 22

opportunity / convenience sampling

Answer 22

sample taken from people wo are available at time of study, who meet criteria

Question 23

advantages of quota sampling

Answer 23

- allows small sample to still be representative of population - no sampling frame needed - quick easy inexpensive - allows easy comparison between different groups in population

Question 24

disadvantages of quota sampling

Answer 24

- non-random sampling can into bias - dividing population into groups can be costly or inaccurate - increasing scope of study increases number of groups adding time / expense - non-responses not recorded

Question 25

advantages opportunity/convenience sampling

Answer 25

easy to carry out inexpensive

Question 26

disadvantages opportunity/convenience sampling

Answer 26

- unlike to provide representative sample - highly dependent on individual researcher