Lecture 4 : Selecting Participants Flashcards
what is a sample? vs a population?
A population is an entire group of people who are the central focus of the study
a sample is a subset of the population
*it is ideal to have the sample be representative of all characteristics of the population
what is probability sampling ?
random sampling- everyone in the population of interest has an equal chance of being selected for the sample
what is non-probability sampling?
everyone in the population does not have an equal chance of being selected to participate in the study; more bias in the participants that are included in the study
What are the four types of probability sampling?
simple random: relies on complete randomization
systematic: orderly way of randomly selecting every nth participant from a sample
ex: every 4th
con= requires an entire list of the entire population
stratified: used when the study is focused on different subgroups of a population; the population is divided into different strata and then participants are selected from those desired strata
cluster: useful when the population is widely spread out. Random groups are made from the population, then participants are randomly selected from those groups
what are the different types of non-probability sampling?
convenience: researchers select any participants who are available to participate in the study even if they are not representative of the population
snowball: used when participants are selected by word of mouth
quota: researches can compare different groups within the population of interest
ex: 60 parents, 30 w/boys 30 w girls. when done, each 30 = a quota
purposive: researcher selects the sample of participants based on their judgement of the “best” participants for the study
Researchers do not always get responses from participants; non responses can be problematic and some contributing facotrs of nonreponses are___________
no times
other responsibilities
langugae barriers
lack of trust
lack of interest
sensitivity to topic
for probability sampling, sample size is primarily determined by what?
error of estimation : likelihood that participants are not representative of the population youre looking at
goal is to have a small error of estimation as possible
inverse relationship to sample size
larger sample size = smaller error of estimation
what is an economic sample
what is power
the degree to which the effects of the independent variable can be detected
impacted by sample size
larger the sample the size the more likely the effect can be detected
what is quota sampling used for?
quota sampling considers population proportions in order to ensure that samples are representative of the population of interest
