when the names of indivisuals participating in a study are not known even to the director of the study
the design of a statistical study shows this if it symmetrically favors certain outcomes
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.
a study that attempts to collect data from every individual in the population.
dividing the population into smaller groups to mirror the characteristics of the population, and choosing an SRS; all individuals should be included in the sample
completely randomized design
when the treatments are assigned to all the experimental units completely by chance
a basic principle of data ethics that requires individual data to be kept private
when two variables are associated in such a way that their effects on a response variable cannot be distinguished from each other.
researchers do this for lurking variables that might affect the response by using a comparitive design and ensuring the only systematic difference between the groups is the treatment administered.
primary purpose is to provide a baseline for comparing the effects of the other treatments. may be given a placebo or an active treatment.
selected by taking the members of the population that are easiest to reach; particularly prone to large bias.
an experiment in which neither the subjects not those who interact with them and measure the response variable know which treatment a subject received.
deliberately imposes some treatment on individuals to measure their responses
the smallest collection of individuals to which treatments are applied.
helps explain or influence changes
the explanatory variables in an experiment are often called this
inference about cause and effect
using results of an experiment to conclude that the treatments caused the difference in responses. requires a well designed experiment where the treatments are randomly assigned to the experimental units.
inference about the population
using information from a sample to draw conclusions about the larger population. requires that the individuals taking part in a study be randomly selected
individuals must be this in advance about the nature of a study and any risk of harm it may bring.
institutional review board
all planned studies must be approved in advance and monitored by this charged with protecting the safety and well-being of the participants.
lack of realism
when the treatments, subjects, or the environment of an experiment are not _____. can limit researchers abitlity to apply the conclusions of an experiment to the settings of greatest interest.
a specific value of an explanatory variable (factor) in an experiment.
not among the explanatory or response variables in a study but may influence the response variable
common form of blocking for comparing just two treatments.
margin of error
a numerical estimate of how far the sample result is likely to be from the truth about the population due to sampling variability.
occurs when a selected individual cannot be contacted or refuses to cooperate; an example of a nonsampling error.
present even in census; examples are nonresponse, response bias, and errors due to question wording.