sampling

Question 1

five types of sampling

Answer 1

• random
• systematic
• stratified
• opportunity
• volunteer

Question 2

define target population

Answer 2

large group of individuals that a particular researcher is interested in studying (subset of general population)

Question 3

what should a sample be

Answer 3

representative of target population so findings can be generalised

Question 4

describe a random sample

Answer 4

• all members of target population have equal chance of being selected

1. obtain complete list of all members of target population
2. all names assigned number
3. sample selected using lottery method

Question 5

describe a systematic sample

Answer 5

• every nth member of target population selected
• sampling frame produced (eg. list of target population organised into alphabetical order)
• sampling system nominated (eg. every 3rd person)

Question 6

describe a stratified sample

Answer 6

• composition of sample reflects proportions of people in subgroups within target/wider population

1. researcher identifies different strata that make up population
2. proportions worked out for representative sample
3. participants which make up each stratum selected by random sampling

Question 7

describe opportunity sampling

Answer 7

• select anyone willing and available to participate at time of study

Question 8

describe volunteer sample

Answer 8

• participants select themselves to be part of sample
• eg. researcher places advert in newspaper/noticeboard

Question 9

evaluate random sampling

Answer 9

+)
P: potentially unbiased
E: confounding or extraneous variables should be equally divided between groups
T: increases internal validity

-)
P: difficult & time-consuming
E: complete list of target population may be difficult to obtain

-)
P: unrepresentative sample
E: eg. may select 20 women from certain area

-)
P: selected participants may refuse to participate

Question 10

evaluate systematic sampling

Answer 10

+)
P: objective
E: once system fro selection established, researcher has no influence over who’s chosen

-)
P: time-consuming & participants may refuse to take part
E: ends up with volunteer sample

Question 11

evaluate stratified sampling

Answer 11

+)
P: produces representative sample
E: designed to accurately represent composition of population
T: findings can be generalised

-)
P: not perfect
E: identified strata cannot reflect all ways people are different
T: complete representation of target population impossible

Question 12

evaluate opportunity sample

Answer 12

+)
P: convenient
E: less costly regarding time & money than other techniques (eg. random sampling), as list of target population not required & no need to divide population into different strata (stratified sampling)

-)
P: suffers from two forms of bias
E: sample unrepresentative of target population as drawn from specific area so findings cannot be generalised to target population & researcher has complete control over selection so may avoid people they don’t like (researcher bias)

Question 13

evaluate volunteer sample

Answer 13

+)
P: easy
E: minimal input from researcher & less time-consuming - also, ends up with more engaged participants

-)
P: volunteer bias
E: may attract certain ‘profile’ of person eg. more curious & wants to please researcher
T: affects how far findings can be generalised