Stats is Awesome!
A variable whose levels are manipulated by the experimenter. Experiments attempt to discover the effects that differences in factor levels may have on the responses of the experimental units.
What is a Factor?
An experiment manipulates factor levels to create treatments, randomly assigns subjects to these treatment levels, and then compares the responses of the subject groups across treatment levels.
What is an experiment?
Individuals on whom an experiment is performed. Usually called subjects or participants when they are human.
What is an experimental unit?
The process, intervention, or other controlled circumstance applied to randomly assigned experimental units. _________ are the different levels of a single factor or as made up of combinations of levels of two or more factors.
What is a treatment?
The experimental units assigned to a baseline treatment level, typically either the default treatment, which is well understood, or a null, placebo treatment. Their responses provide a basis for comparison.
What is a control group?
An observational study in which subjects are followed to observe future outcomes. Because no treatments are deliberately applied, prospective study is not an experiment. Nevertheless, prospective studies typically focus on estimating differences among groups that might appear as the groups are followed during the course of study.
What is a prospective study?
A variable whose values are compared across different treatments. In a randomized experiment, large response differences can be attributed to the effect of differences in treatment level.
What is a response?
The specific values that the experimenter chooses for a factor are called the ______ of the factor.
What are the levels?
In a completely randomized design, all experimental units have an equal chance of receiving any treatment.
What is a completely randomized design?
When an observed difference is too large for us to believe that it is likely to have occurred naturally, we consider the difference to be __________ _________. Subsequent chapters will show specific calculations and give rules, but the principle remains the same. (p. 312)
What is statistically significant?
Any individual associated with an experiment who is not aware of how subjects have been allocated to treatment groups is said to be _______. (p. 314)
What is blinding?
A treatment known to have no effect, administered to one group so that all groups experience the same conditions. Many subjects respond to such a treatment (a response known as a placebo effect). Only by comparing with a placebo can we be sure that the observed effect of a treatment is not due simply to the placebo effect. (p. 316)
What is a placebo?
The tendency of many human subjects (often 20% or more of experiment subjects) to show a response even when administered a placebo. (p. 316)
What is a placebo effect?
In a randomized block design, the subjects are randomly assigned to treatments only within blocks. (p. 317)
What is randomized block design?
In a retrospective or prospective study, subjects who are similar in ways not under study may be matched and then compared with each other on the variables of interest. Matching, like blocking, reduces unwanted variation. (p. 317)
What is matching?
To be valid, an experiment must assign experimental units to treatment groups at random. (p. 307)
What is random assignment?
An observational study in which a researcher looks back to analyze an experiment that has already taken place.
What is a retrospective study?
When groups of experimental units are similar, it is often a good idea to gather them together into blocks. By blocking, we isolate the variability attributable to the differences between the blocks so that we can see the differences caused by the treatments more clearly. (p. 317)
What is blocking?
When the levels of one factor are associated with the levels of another factor in such a way that their effects cannot be separated, we say that these two factors are __________. (p. 319)
What is confounding?
Usually thought of as a variable associated with both y and x that makes it appear that x maybe causing y.
What is a lurking variable?
Can we say that a factor is the cause for a certain result in an experiment?
What is No?
There are two main classes of individuals who can affect the outcome of an experiment:
■ those who could influence the results (the subjects, treatment administrators, or technicians).
■ those who evaluate the results (judges, treating physicians, etc.).
When every individual in either of these classes is blinded, an experiment is said to be single-blind. When everyone in both classes is blinded, we call the experiment double-blind. (p. 315)
What is single and double blind?
Is there a difference between an observational study and an experiment?
What is yes?
What is the difference between an observational study and an experiment?
Give answer.
Control, Randomization, Replication, and Blocking.
What are principles of experimental design?