Sample types
Choosing individuals who are easiest to reach results from
Convenience sample
the entire group of individuals about which we want information
Population
When an individual chosen for the sample can’t be contacted/refuses to participate
Nonresponse
When individuals are observed and data is collected but the variable of interest is not influenced.
Observational Study
A condition applied to individuals in an experiment
Treatment
People who choose themselves to be in a study by responding to a general appeal
Voluntary Response Sample
The part of the population from which we collect information to draw conclusions about the entire populations
Sample
When some groups in the population are left out of the process of choosing the sample
Undercoverage
Imposes a treatment on individuals and their responses to treatments are recorded
Experiment
When some subjects respond favorably to any treatment, even a placebo
Placebo effect
This type of sample uses a chance process so that every individual has an equal chance to be selected
Simple Random Sample
Systematically favoring certain outcomes
Bias
When an individual gives the wrong response or lies about their answer
Response bias
In order to generalize the results of a study to a population, the sample must be selected using this process
Random / Simple Random Sample
Can be an inactive treatment group or a group that receives no treatment
Control Group
I am collecting this type of sample if I want to find out how many cat owners buy wet food, and I survey the first 100 people that walk into a pet store.
Convenience sample
A treatment that has no active ingredient, but is otherwise like other treatments
Placebo
An outside factor besides the explanatory variable that may cause changes in the response variable
Confounding variable
In order to show causation, treatment groups must be created using this process
Random assignment
Both the subject and the person measuring the response are unaware of what treatment was assigned
Double Blind