Chapter 5: Selecting Research Participants

Ultimately, the researcher is interested in the behavior/phenomenon of the entire ______

population

define sampling

process of selecting participants for a research project

(bigger/smaller) samples may be unrepresentative of the population

smaller

define the accessible population

members of the total population that are accessible to be recruited

define a biased sample

sample participants differ from population on a given characteristic

when can we say that selection isn’t random

when selection favors the inclusion of certain participants 

define the law of large numbers

the larger the sample size the more accurately it will represent the population

define statistical power 

formula which identifies the minimum number of participants needed to detect an expected effect in a study

in which type of sampling is the size of the population unknown

nonprobability sampling

define simple random sampling

random process to select individuals from a list where all members of population are described 

if the population is small it is favorable to sample (with/without) replacement

with

are the following data sets concurrent with replacement or non-replacement sampling: 

• bootstrapping dataset

• cross-validation studies

• bootstrapping: with replacement

• cross-validation: without replacement

systematic random sampling ensures a ____ degree of representativeness

high

True or false? systematic random sampling is a completely independent sampling method

false, because sample follows an order caused by the first chosen participant, it is inherently dependent

define stratified random sampling  

selection procedure dividing population into strata and selecting a random sample from each stratum 

in stratified sampling, is the sample representative of the population

no

in proportionate stratified sampling, is the sample representative of the population

yes

_____ sampling is used when the population is not completely known

nonprobability

name the types of non probability sampling

1. convenience sampling 

2. quota sampling 

3. snowball sampling 

what is the main problem with non probability sampling 

no evidence they are representative

define convenience sampling/ accidental sampling

selection of participants based on accessibility and convenience

in ______, participants are chosen based on availability and willingness

convenience sampling

how can a researcher limit the loss of validity in convenience sampling

1. use a large sample with broad cross-section of individuals 

2. provide detailed description of sample so people can draw inferences about generalizability 

define quota sampling 

formation of a sample from fulfilling strict quotas for relevant categories of participants 

True or false, in quota sampling, the chosen sub groups should be reflective of the proportions in the population

false, they can also be equally represented 

in quota sampling, participants are selected based on (random selection/convenience)

convenience 

define snowball sampling

use of a current participants to reach other potential participant

why is snowball sampling usually used

due to difficulty of recruitment with certain populations