Statistics - Chapter 9

statistically significant

An observed effect so large that it would rarely occur by chance is called what?

control, randomize, replication

What are the 3 principles of experimental design?

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

matched-pairs design

a randomized experimental design in which—within each matching pair of similar subjects—chance is used to determine which subject gets each treatment

lurking variable

a variable that is not among the explanatory or response variables in a study but that may influence the response variable

completely randomized design

an experiment in which all the subjects are allocated at random among all the treatments

double-blind experiment

an experiment in which neither the subjects nor those who interact with them and measure the response variable know which treatment each subject is receiving

comparative experiment

an experiment in which some individuals receive one treatment and similar units receive another

randomized comparative experiment

an experiment that uses both comparisons of two or more treatments and random assignment of subjects to treatments

treatment

any specific experimental condition applied to the subjects - if an experiment has more than one factor, is a combination of specific values of each factor

experiment

deliberately imposes some treatment on individuals to observe their responses - the purpose is to study whether the treatment causes a change in the response

factors

explanatory variables in an experiment

subjects

individuals studied in an experiment

random assignment

means that individuals are assigned to treatments at random, that is, using some sort of chance process

observational study

observes individuals and measures variables of interest but does not attempt to influence the responses - the purpose is to describe some group or situation

confounding

occurs when two variables are associated in such a way that their effects on a response variable cannot be distinguished from each other

control group

receives an inactive treatment or an existing baseline treatment

block design

the random assignment of experimental units to treatments is carried out separately within each block