chapter 9: Producing data, experiments Flashcards
observational study
observes individuals and measures variables of interest, but does not attempt to influence the responses. The purpose of an observational study is to describe some group or situation.
experiment
deliberately imposes some treatment on individuals to observe their responses. The purpose of an experiment is to study whether the treatment causes a change in the response.
When our goal is to understand cause and effect, ____________ are the preferred source for fully convincing data.
experiments
factor
another name for an explanatory variable in an expermient
randomized comparative experiments
designed to give good evidence that differences in the treatments actually cause the differences we see in the response
replication
the use of enough subjects to reduce chance variation
three principles of experimental design
control (restrict lurking variables), randomization (use of chance), replication (enough subjects)
statistical significance
when an observed effect is so large that it would rarely occur by chance
matched pairs design
when you randomize within each pair (helps eliminate bias that might occur from the order of the treatments)
double blind experiment
neither the subjects nor the people who interact with them know which treatment each subject is receiving.
Lack of blindness in an experiment can ____________ how far the results can be generalized
greatly impact
a block
a group of individuals that are known before the experiment to be similar in some way that is expected to affect the response to the treatments
block design
the random assignment of individuals to treatments is carried out separately within each block.
the difference between an observational study and an experiment is
in an observational study individuals self-select, versus being chosen at random
