4.2 stats

block

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

matched pairs design

a method of assigning subjects to groups in which pairs of subjects are first matched on some characteristic and then individually assigned randomly to groups OR common form of blocking for comparing just two treatments

treatment

a specific condition applied to the individuals in an experiment

explanatory variable

a variable that we think explains or causes changes in the response variable (sometimes called factors)

double blind experiment

an experiment in which neither the experimenter nor the participants know which participants received which treatment

single-blind experiment

an experiment in which one party knows which treatment they are receiving, and the other doesn't

statistically significant

an observed effect so large that it would rarely occur by chance

experiment

deliberately imposes some treatment on individuals to measure their responses

random assignment

experimental units are assigned to treatments using a chance process

control

in an experiment, the standard that is used for comparison

response variable

measures an outcome of a study

observational study

observes individuals and measures variables of interest but does not attempt to influence the responses

confounding

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

completely randomized design

the experimental units are assigned to the treatments completely by chance

randomized block design

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

experimental units

the smallest collection of individuals to which treatments are applied

level

the specific values that the experimenter chooses for a factor

replication

use enough experimental units in each group to distinguish a difference in the effects of the treatments from chance variation due to the random assignment