Sampling

Question 1

what is sampling?

1

Answer 1

the method used to select participants to take part in the study

Question 2

sample taken should represent…

3

Answer 2

the type of people in the target population, which is the group of people the researcher is interested in generalising their findings to

e.g. people in the UK, young people living in london

allows generalisations about the population to be made

Question 3

5 types of sampling

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Answer 3

opportunity

volunteer

stratified

systematic

random

Question 4

what is opportunity sampling?

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Answer 4

use whoever is immediately available, most convenient and willing to take part at the time of the study

e.g. people in your school or passers by on the street

Question 5

advantages of opportunity sampling

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Answer 5

easiest way to get participants, just use first suitable people you find so you don’t spend as much time locating your sample

therefore saves time and money

Question 6

disadvantages of opportunity sampling

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Answer 6

inevitably bias and harder to generalise as it only has participants from a specific and small part of the population

sample may also be bias as researcher may have chosen a specific area to prove their point

e.g. if you select your sample from people in town in a monday morning then it would be unlikely to include professional people because they’d be working and unlikely to include people from rural areas because they live further away

Question 7

what is random sampling?

2

Answer 7

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

selected randomly using a computer generator

Question 8

advantages of random sampling

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Answer 8

least likely to have sample bias as all members of the sample have an equal chance of selection

Question 9

disadvantages of random sampling

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Answer 9

time consuming — need to have a list of all the members of the population and then contact everyone selected, asking if they wish to take part

a lot of people may decline to take part, which means that building a sufficient sample takes even more time

Question 10

what is stratified sampling?

3

Answer 10

identify subgroups within a population (age groups, gender, etc)

participants are obtained from each group in proportion to their occurrence in the population

selection from each subgroup is done randomly

Question 11

advantages of stratified sampling

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Answer 11

likely to be much more representative of the target population due to proportional representation of subgroups

therefore more easy to generalise to the target population

Question 12

disadvantages of stratified sampling

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Answer 12

more time consuming as you have to identify subgroups, randomly select participants and contact them

many might decline to take part, meaning you have to keep asking until you have enough participants

Question 13

what is systematic sampling?

3

Answer 13

participants are selected systematically from the population

selecting every nth person from the list, usually starting at a random number — e.g. every 6th person on the list is selected, starting at the 8th name down and this numerical interval is applied consistently

may select such names from a phonebook

Question 14

advantages of systematic sampling

1

Answer 14

unbiased as participants are selected using an objective system

Question 15

disadvantages of systematic sampling

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Answer 15

more time consuming

not truly unbiased or random unless you select a number using a random method and start at that number, selecting every nth person

Question 16

what is volunteer sampling?

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Answer 16

use whoever puts themselves forward through an advertisement in a newspaper, notice board or on the internet

relies solely on people volunteering to be a part of the sample

Question 17

advantages of volunteer sampling

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Answer 17

less likely to drop out as they’ve signed up for it and know what they have to do, people who volunteer are likely to be more highly motivated and enthusiastic about taking part

gives access to a variety of participants, for example everyone who reads a certain newspaper, especially true if you’ve advertised on more than one platform, may lead the sample to be more representative and less biased

Question 18

disadvantages of volunteer sampling

2

Answer 18

increased demand characteristics as they’re more motivated and enthusiastic about taking part, they might try to be helpful or appear a certain way so change their behaviour — demonstrates that the sample is biased in other ways, mainly volunteer bias

might not be representative of the population as the method of advertisement may only attract a certain type of person e.g. advertising on the internet may only attract younger people

Question 19

what is bias?

4

Answer 19

a systematic distortion

EXAMPLES = experimenter bias, interviewer bias, observer bias, social desirability bias, sample bias, volunteer bias

sample bias describes a sample that is inevitably biased or distorted because it is not truly representative of the population

volunteer bias describes the idea that people who volunteer are likely to be different to other members of the population, they may be more highly motivated for example, this distorts or biases the data they produce as they may not be representative of the population

Question 20

what is generalisation?

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Answer 20

applying the findings of a particular study to the population that the researcher is interested in

Question 21

what is volunteer bias?

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Answer 21

a form of sampling bias

volunteer participants have special characteristics — they tend to be more highly motivated than randomly selected participants

alternatively, they may be quite financially insecure so need the money offered for participation

Question 22

random techniques used in random sample

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Answer 22

THE LOTTERY METHOD — obtain a list of all the people in the population, put all these names in a hat, draw the number of names required out of the hat, use these as participants

RANDOM NUMBER GENERATOR — number every member of the population, may use a computer programme such as microsoft excel to type =RAND(100) to get a random number between 1 and 100, repeat this until you’ve selected enough people for your sample