sampling

Question 1

what does the term ‘population’ refer to?

Answer 1

a group of people who are the focus of the researcher’s interest, from which a smaller sample is drawn. this is often called a target population because it is a subset of the general population

Question 2

what is a sample?

Answer 2

a group of people who take part in a research investigation. the sample is drawn from a target population and is presumed to be representative of that population

Question 3

what is a random sample?

Answer 3

where all members of the target population have an equal chance of being selected

Question 4

how can a random sample be obtained?

Answer 4

1. obtain a complete list of all members of the target population
2. all names on list are assigned a number
3. actual sample is selected through use of lottery method eg. picking numbers from a hat

Question 5

what is a systematic sample?

Answer 5

when every nth member of the target population is selected eg. every 3rd house on a street

Question 6

how can a systematic sample be obtained?

Answer 6

• a sampling frame is produced, which is a list of people in the target population organised eg. into alphabetical order
• a sampling system is nominated (every 3rd etc.)
• may begin from a randomly determined start to reduce bias
• researcher then works through the sampling frame until the sample is complete

Question 7

what is a stratified sample?

Answer 7

where the composition of the sample reflects the proportions of people in certain subgroups (strata) within the target or wider population

Question 8

how can a stratified sample be obtained?

Answer 8

1. identify the different strata that make up the population
2. proportions needed for the sample to be representative are worked out
3. the participants that make up each stratum are selected using random sampling

Question 9

what is an opportunity sample?

Answer 9

when researchers select anyone who happens to be willing and available

Question 10

how can an opportunity sample be obtained?

Answer 10

the researcher takes the chance to ask whoever is around at the time of their study eg. stopping people on the street

Question 11

what is a volunteer sample?

Answer 11

when participants select themselves to be part of the sample. hence, it is also referred to as self-selection

Question 12

how can a volunteer sample be obtained?

Answer 12

• researcher may place an advert in a newspaper or on a common room noticeboard
• willing participants may raise their hand when the researcher asks

Question 13

strengths of random sampling

Answer 13

• potentially unbiased
• confounding or extraneous variables should be equally divided between the different groups, enhancing internal validity

Question 14

limitations of random sampling

Answer 14

• difficult and time-consuming to conduct
• a complete list of the target population may be extremely difficult to obtain
• you may still end up with a sample that is unrepresentative
• selected participants may refuse to take part, so you may end up with something more like a volunteer sample (applies to all)

Question 15

evaluation of systematic sampling

Answer 15

+ objective. once the system for selection has been established, the researcher has no influence over who is chosen, which is even more the case if the start is randomly selected
- time consuming
- participants may refuse to take part, resulting in a volunteer sample

Question 16

evaluation of stratified sampling

Answer 16

+ representative sample as it is designed to accurately reflect the composition of the population
> this means generalisation of findings becomes possible
- stratification is not perfect
> the identified strata cannot reflect all the ways that people are different, so complete representation of the target population is not possible

Question 17

evaluation of opportunity sampling

Answer 17

+ convenient. costs less time and money as a list of members of target population is not required and no need to divide members into strata
- 1st bias: unrepresentative of target population as it is drawn from a very specific area, so findings cannot be generalised to target population
- researcher bias. researcher has complete control over the selection of participants and may eg. avoid people they do not like the look of

Question 18

evaluation of volunteer sampling

Answer 18

+ easy
> requires minimal input from researcher and so is less time-consuming than other forms of sampling
+ researcher ends up with participants who are more engaged
= volunteer bias. asking for volunteers may attract a certain people eg. one who is curious and more likely to try and please the researcher (demand characteristics), which impacts how far findings can be generalised