Lecture 5 Flashcards
(16 cards)
Sampling:
It’s usually not practical to obtain data from your entire population, so you must…
This is an issue of external validity:
It is important that the sample be…
sample from the population.
to what degree can you generalize the findings to a larger group?
representative of the population.
Sampling Frame:
If you can’t afford to sample everyone in your population…
For example:
Population:
Sampling frame:
Sample:
focus on a subset of the population to draw your sample.
children in NZ
children in Wellington
a subset of children in Wellington
Population:
Sampling frame:
Sample:
the group to which I want to generalise (goats)
the group from which I obtained my sample (goats from sanctuary)
the group from which I obtained data (10 goats)
Sample Size
Statistical power
Depends on what you want to do with your data
Probability Sampling:
tends to be…
There are three types:
expensive, time-consuming, but it’s better than non-probability sampling.
Simple random
Stratified random
Cluster
Probability Sampling:
Simple random sampling:
Stratified random sampling:
Cluster sampling:
every person in the population has an equal chance of being sampled.
divide population along dimensions (e.g., gender, SES, ethnicity, etc.), and be sure that you sample proportionately across these dimensions.
obtain participants from pre-existing groups or clusters. Try to get a random sample of clusters.
Nonprobability Sampling:
tends to be…
There are four types:
cheaper and easier, but you worry about representativeness.
Convenience
Quota
Purposive
Snowball
Nonprobability Sampling:
Convenience sampling:
Quota sampling:
Purposive sampling:
Snowball sampling:
Sample from readily available sources. Handy for the researcher. Biases are introduced.
obtain appropriate percentages of different types of participants (e.g., gender, ethnicity), but one is still obtaining these participants from readily available sources.
you select individuals who fit within a particular category to fit a purpose.
recruit an initial group of participants, and then you obtain referrals from them to obtain data from their friends and acquaintances. Useful for rare types of participants (e.g., surfers).
What do most people do?
Most research psychologists use…
Is this defensible?
Pay attention to samples when you read research:
- Who is the most commonly sampled population in Psychology research?
nonprobability sampling (it costs a lot of money, time, and effort to obtain probability samples)
Depends on the situation.
Western Educated Industrial Rich Democratic and University Students
Biases:
Non-representativeness of the sample:
Self-selection bias:
Ethics:
when the sampling frame significantly differs from the population, you have introduced biases.
When you have a low response rate, who are the participants you get?
If you’re studying children and adolescents and only obtain about 60% parental permissions, what are the other 40% like?
Creative Approaches: Passive ethical consent for... Compensation and... Interesting ways to collect data: Interviews. Underutilised samples
children and adolescents
inducements
laptops or iPads; internet; testing on cell phones; diary studies; etc.
e.g., from school to after-school program, to avoid survey fatigue (people don’t want to answer lots of surveys) and increase motivation
Role of Technology:
Technology is…
Observations of naturally occurring behaviour;
Through cell phones and tablets (multi-media portable computers);
Through surveillance of one’s use of technological devices.
Questions of ethics will continue to be important!
increasing our access to information
Event Sampling Method (ESM):
Captures data on an hourly, daily, or weekly basis.
Good for rapidly changing variables on relatively small samples.
“The experience sampling method, also referred to as a daily diary method, is an intensive longitudinal research methodology that involves asking participants to report on their thoughts, feelings, behaviors, and/or environment on multiple occasions over time.”
ESM: Advantages
Capturing phenomena nearer the time that they occur:
Obtaining multiple assessments of variables of interest, and…
Can identify…
better memory for events, feelings, and thoughts
more assessments of a construct yield better reliability and validity
contexts for important psychological states
ESM: Disadvantages Difficult to recruit and retain individuals who... Participants must be... Lots of... Difficult to...
don’t mind that their day is interrupted by signals to report states
comfortable with the recording device
missing data
analyse this type of data: numerous repeated measures
Conclusions:
Try to use or approximate representative sampling—your data will generalise to the population better
Be aware of biases that can creep in due to your recruitment procedures
Technology is enabling new methods of data collection, but be aware of new pitfalls
ESM methods are powerful and flexible, but data analysis is challenging
