Sampling

Question 1

What is a population?

Answer 1

the group we are interested in knowing more about

Question 2

What is a sample?

Answer 2

The group of individuals chosen from the population to represent it in a research study

Question 3

What is a target population/sampling frame?

Answer 3

Refers to the population from which we will sample, but is more specific than vague population

Question 4

What is a representative sample>

Answer 4

sample contains sub-groups of people in direct proportion to their prevalence in general population - sample accurately reflects characteristics of the population.
Expected to represent behaviours and attitudes of population we want to study

Question 5

What is external validity?

Answer 5

The extent to which the results of one study can be generalised across settings, time and populations

Question 6

What is generalisation?

Answer 6

The process of extrapolating the results

Question 7

What is sampling bias?

Answer 7

selection bias - systematic tendency towards over or under-representation of some categories in a sample

Question 8

What is a biased sample?

Answer 8

A sample in which members of a sub-group of larger population are over/under-represented

Question 9

What is sampling error?

Answer 9

Any difference in the observations between the sample and population
- all research studies have some sampling error because the sample will never give the same observations as the entire population.
- the best we can do is minimise the sampling error as much as possible

Question 10

What is standard error (SE)?

Answer 10

Measures how well the mean of a particular sample represents the mean of the population

Question 11

What does a small standard error indicate?

Answer 11

Sample means are similar to population mean and the sample is likely to be an accurate reflection of the population

Question 12

What is the equation for standard error?

Answer 12

SE = standard deviation / square root of the number of samples

Question 13

What are 2 ways to reduce sampling errors?

Answer 13

• larger sample (needs to be representative)
• Choose a sampling technique that gives you the most representative sample for the population you want to study.

Question 14

What are the 2 types of sampling?

Answer 14

• probability sampling
• non-probability sampling

Question 15

What is probability sampling?

Answer 15

There is a specific/known probability of each member of the population being sampled
- requires a clearly defined population we can have access to
- most likely representative of whole population - should use wherever feasible
- can reduce sampling error

Question 16

What is non-probability sampling?

Answer 16

There is NOT a specific and known probability of each member of the population being sampled
- often used in psych research
(often interested in identifying trends and relationships between variables)
- individuals not chosen randomly

Question 17

What are 4 examples of probability sampling?

Answer 17

• simple random sampling
• systematic random sampling
• stratified sampling
• cluster sampling

Question 18

What are 4 examples of non-probability sampling?

Answer 18

• convenience sampling
• purposive sampling
• quota sampling
• snowball sampling

Question 19

What is simple random sampling?

Answer 19

Probability sample
A sample is chosen randomly from population so everyone has an equal chance of being selected
- reduces sampling error by choosing from all members of population to represent it
- sample units are selected randomly

Question 20

What is one way to achieve simple random sampling?

Answer 20

The lottery method
- computer selection/random number tables/manual selection (each unit in population assigned a number, written on a piece of paper and put in a hat)

Question 21

What is systematic random sampling?

Answer 21

Probability sample
Requires selecting samples based on a system of intervals in a numbered population
- random starting point but with a fixed, periodic interval
- Sample selected by taking every nth case from a list of target population (eg. every 5th)
- Sample units selected systematically via a single technique

Question 22

What is stratified sampling?

Answer 22

Probability sample
Determine groups (strata) within population whose proportions we want the sample to reflect - enhances representativeness
- divide population into groups
- proportion of group in sample should be equal to proportion of group in population
- reduces bias
- similar to simple random

Question 23

What is cluster sampling?

Answer 23

Probability sample
Clusters of individuals are identified then a subset of clusters is randomly chosen to sample from
- sample chosen randomly from clusters identified in population
- makes it easier to choose members randomly from smaller clusters to better represent population
- can ignore segments of population not in clusters chosen for sample

Question 24

What is convenience sampling?

Answer 24

Non-probability sample
A sample is chosen from people who are available to participate in the research
AKA availability sampling or volunteer sample
- available to researcher, respond to an ad or volunteer
- used in many psych experiments

Question 25

What is purposive sampling?

Answer 25

Non-probability sample
Researchers rely on their judgement when choosing members of population to participate in study
- sample consists of people who have a particular set of characteristics that are relevant to the study
AKA judgement, selective or subjective sampling

Question 26

What is quota sampling?

Answer 26

non-probability sampling
Similar to stratified except uses non-probabilistic sampling technique
- identify relevant characteristics of units and their percentage in the population (quotas) and then apply convenience sampling to fill quotas
- representative

Question 27

What is snowball sampling?

Answer 27

non-probability sample
Can be used by researchers looking for a specialised population
- used for research with hidden populations, excluded communities or invisible groups
- past ppts recommend future ppts from same population
- introduces bias into sample (not representative)

Question 28

What are WEIRD populations?

Answer 28

W - Western
E - Educated
I - Industrialised
R - Rich
D - Democratic
Highly represented in psychological research - persistent sampling bias

Question 29

What is non-response bias?

Answer 29

Can lead to non-representative sample of individuals who refuse to participate in study
eg. unhappy couples refuse to participate in study about marriage

Question 30

How can sampling bias relate to culture?

Answer 30

Samples may not be comparable and variations in samples from one cultural context to the other can confound observer scores