AP statistics collecting data
A stratified random sample addresses the same issues as
A block design
Simple Random Sample (SRS)
A method of sampling that allows for every possible combination of individuals have equal likelihood of selection
Cluster Sample
A method whereby subjects are divided into groups that are very similar to each other. Then one or more entire groups are selected randomly for samplinh
Stratified Random Sample
A method whereby subjects are sorted into group with common traits before sampling. Then an SRS is taken from each group or strata to form the sample
Undercoverage
A sample that excludes certain members of a population from the selected process
Simple Random Sample
A sample that gives every possible sample of the same size the same chance to be selected
Bias
A study or experiment that systemically favors a particular outcome either intentionally or accidentally
Sample Survey
A study that collects data from a sample that is chosen to represent a specific population
voluntary response sampling
A system that allows subjects to choose to be in the sample by responding to a general invitation
Census
Collecting data from every individual in the population
The purpose of double blind experiment is to
Eliminate a possible source of bias
Experimental unit
Is the object to which a treatment is randomly assigned
Control group
Is used to provide a baseline for comparing the effects of other trestments
Statistically Significant
It is so unlikely to hallen by random chance
Double blindside
Neither the subjects nor those who interact with them and measure the response variable know which treatment a subject received
Observation study
No treatment, no cause and effect, confunding effect,
Observational stidy
Observes individuals and measures variables of interest but does not attempt to influence the responses
Non- response bias
Occurs if an individual chosen for the sample can't be contacted or refuses to be contacted
Response bias
Occurs if there is a systematic pattern of selected individuals giving inaccurate or untruthful responses
Word bias
Occurs when a question leads subjects to respond in a particular way
In an experiment an observed effect so large that it would rarely occur by chance is called
Statistically significant
Subjects
The experimental units are human being
Stratified random sample is appropriate when
The population can be easily subdivided into groups according to some categorical variable, and the variable you are measuring is very similar within the groups but quite different between groups
Matches pairs design
Two similar experimental units are paired and two treatments are randomly assigned within each pair
Sample
a subset of individuals in the population from which we actually collect data (mostly humans)
Explanatory variable
may help explain or influence changes in a response variable
Response variable
measures an outcome of a study
Confounding
occurs when two variables are associated in such a way that their effects on a response variable cannot be distinguished from each other
single-blind experiment
subjects do not know which treatment they are receiving
Population
the entire group of individuals we want information about
Randomized block design
the random assignment of experimental units to treatments is carried out separately within each block
