Data Collection
a type of random sample in which every member of the population has an equal and independent chance of being selected. This is the most basic and unbiased sampling method
What is SRS?
Occurs if poor wording of question results in lack of clarity or if question presents only one side of argument
What is poor wording bias?
The individuals or objects that are being studied.
What are experiemntal units?
The purpose of randomness in an experiment
Increase validity of the experiments and decreases effects of bias
Statistical association or relationship between two or more variables
What is correlation?
When an item from a population can be selected only once. This means that once an item has been selected, it is not replaced back into the population and is no longer available for selection.
What is "sampling without replacement" ?
Occurs when some individuals who are A PART of the survey do not respond
What is nonreposnse bias?
The variable that is manipulated by the experimenter
What is the explanatory variable?
Purpose of replication in an experiment
To reduce variablility and increase confidence
a substance or treatment that has no therapeutic effect
What is a placebo?
a type of random sample in which the population is divided into subgroups (strata) based on certain characteristics, and a separate random sample is drawn from each stratum.
What is a stratified SRS?
the tendency of a person to answer questions on a survey untruthfully or misleadingly
What is reponse bias?
The variable that is being measured
What is the repsonse variable?
Purpose of a control group
To be able to tell the effects of what you are testing. Without a control group you have no experiment.
when the subjects in an experiment do not know if they are in the treatment or control group
What is single blind?
the population is divided into groups, and a random sample of groups are selected. All members of the selected groups are included in the sample. This method is often used when it is impractical or too expensive to sample the entire population individually
What is a cluster sample?
A portion of the population has been excluded from the sample or is not proportionally represented to how it is in the population.
What is undercoverage bias?
Variable that may influence the relationship between the explanatory and response variables
What is a confounding variable?
Purpose of a placebo
To see the effects of the experiment without any influcences.
when the subjects as well as those evaluating the result of an experiment do not know which subjects are in the treatment or control groups
what is double blind?
A type of random sample in which the members of the population are listed in some order, and every nth member is selected for the sample, where n is the sampling interval.
What is a systematic random sample?
bias where only those who are passionate (strongly against or for) respond to the surveys/attend meetings/express opinions.
What is voluntary bias?
A false association between the explanitory and response variable
What is the effect of a counfounding variabale on an expieriment?
Purpose of blocking
Block designs help maintain internal validity
attempting to survey the entire population
what is a census?