Unit 4 Flashcards
The entire group of individuals we want information about
Population
Collects data from every individual in the population
Census
A subset of individuals in the population from which we collect data
Sample
A study that collects data from a sample to learn about the population from which the sample was selected
Sample Survey
Selects individuals from the population who are easy to reach
Convenience Sampling
A study shows this if it is very likely to underestimate or very likely to overestimate the value you want to know
Bias
Allows people to choose to be in the sample by responding to a general invitation
Voluntary Response Sampling
Involves using a chance process to determine which members of a population are included in the sample
Random Sampling
Chosen in such a way that every group of individuals in the population has an equal chance to be selected as the sample
Simple Random Sample (SRS)
An individual from a population can be selected only once
Sampling Without Replacement
An individual from a population can be selected more than once
Sampling With Replacement
Groups of individuals in a population who share characteristics thought to be associated with the variables being measured in a study
Strata
Selects a sample by choosing an SRS from each stratum and combining the SRSs into one overall sample
Stratified Random Sampling
A group of individuals in a population that are located near each other
Cluster
Selects a sample by randomly choosing clusters and including each member of the selected clusters in the sample
Cluster Sampling
Selects a sample from an ordered arrangement of the population by randomly selecting one of the first k individuals and choosing every kth individual thereafter
Systematic Random Sampling
Occurs when some members of the population are less likely to be chosen or cannot be chosen in a sample
Undercoverage
Occurs when an individual chosen for the sample can’t be contacted or refuses to participate
Nonresponse
Occurs when there is a systematic pattern of inaccurate answers to a survey question
Response Bias
Observes individuals and measures variables of interest but does not attempt to influence the responses
Observational Study
Measures the outcome of a study
Response Variable
May help explain or predict changes in a response variable
Explanatory Variable
Occurs when two variables are associated in such a way that their effects on a response variable cannot be distinguished from each other
Confounding
Deliberately imposes treatments on individuals to measure their responses
Experiment
A treatment that has no active ingredient, but is otherwise like other treatments
Placebo
A specific condition applied to the individuals in an experiment
Treatment
The object to which a treatment is randomly assigned
Experimental Unit
Term given to experimental units that are human beings
Subjects
An explanatory variable that is manipulated and may cause a change in the response variable
Factor
Different values of a factor
Levels
Used to provide a baseline for comparing the effects of other treatments
Control Group
Describes the fact that some subjects in an experiment will respond favorably to any treatment, even an inactive treatment
Placebo Effect
Neither the subjects nor those who interact with them and measure the response variable know which treatment a subject is receiving
Double-Blind
Either the subjects or the people who interact with them and measure the response variable don’t know which treatment a subject is receiving
Single-Blind
Experimental units are assigned to treatments using a chance process
Random Assignment
Keeping other variables constant for all experimental units
Control
Giving each treatment to enough experimental units so that a difference in the effects of the treatments can be distinguished from chance variation due to the random assignment
Replication
The experimental units are assigned to the treatments completely at random
Completely Randomized Design
A group of experimental units that are known before the experiment to be similar in some way that is expected to affect the response to the treatments
Block
The random assignment of experimental units to treatments is carried out within each block
Randomized Block Design
A common experimental design for comparing two treatments that uses blocks of size 2
Matched Pairs Design
Refers to the fact that different random samples of the same size from the same population produce different estimates
Sampling Variability
When the observed results of a study are too unusual to be explained by chance alone
Statistically Significant
