Vocab 1
In a statistical study, the entire group of individuals we want information about.
population
This is the value we use for the boundary between what could happen by chance alone and what is statistically significant.
5%
Grouping individuals by area then sample every individual in a selected group.
Occurs when some members of the population are less likely to be chosen or cannot be chosen in a sample.
Undercoverage
Experimental group whose primary purpose is to provide a baseline for comparing the effects of the other treatments. Depending on the purpose of the experiment, a control group may be given an inactive treatment, an active treatment, or no treatment at all.
control group
Study that collects data from every individual in the population
census
Study that observes individuals and measures variables of interest but does not attempt to influence the responses.
Observational Study
Assign numbers to every individual in the data set then use a random number generator to make selections.
Sample chosen in such a way that every group of n individuals in the population has an equal chance to be selected as the sample
simple random sample (SRS)
A treatment that has no active ingredient but is otherwise like other treatments.
Placebo
When the observed results of a study are too unusual to be explained by chance alone, the results are called...
statistically significant
All individuals who are subjects in a study must give this before data is collected.
informed consent
Group individuals by specific characteristics then select some individuals from every group.
stratified sample
The design of a statistical study shows this if it is very likely to underestimate or very likely to overestimate the value you want to know.
bias
Specific condition applied to the individuals in an experiment. If an experiment has several explanatory variables, a treatment is a combination of specific values of these variables.
Treatment
Subset of individuals in the population from which we collect data
sample
A study in which researchers deliberately impose treatments (conditions) on individuals to measure their responses.
experiment
Assign numbers to every individual in the data set then randomly select an integer k and sample every kth individual.
systematic
Occurs when an individual chosen for the sample can't be contacted or refuses to participate.
nonresponse
When two variables are associated in such a way that their effects on a response variable cannot be distinguished from each other.
confounding
The fact that different random samples of the same size from the same population produce different estimates.
sampling variability
Sample that consists of people who choose to be in the sample by responding to a general invitation.
Sample that consists of individuals from the population who are easy to reach.
convenience sample
Occurs when there is a consistent pattern of inaccurate responses to a survey question. Includes bias due to question wording, lack of anonymity, and characteristics of the interviewer.
response
The object to which a treatment is randomly assigned. When these are human beings, they are often called subjects.
experimental units