Chapter 13

Question 1

Observational study

Answer 1

a study based on data in which no manipulation of factors has been employed

Question 2

Retrospective study

Answer 2

an observational study in which subjects are selected and then their previous conditions or behaviors are determined

Question 3

Prospective study

Answer 3

an observational study in which subjects are followed to observe future outcomes

Question 4

Experiment

Answer 4

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

Question 5

Random assignment

Answer 5

To be valid, an experiment must assign experimental units to treatment groups at random

Question 6

Factor

Answer 6

a variable whose levels are manipulated by the experimenter

Question 7

Response

Answer 7

a variable whose values are compared across different treatments

Question 8

Experimental units

Answer 8

individuals on whom an experiment is performed

Question 9

Level

Answer 9

the specific values that the experimenter chooses for a factor

Question 10

Treatment

Answer 10

the process, intervention, or other controlled circumstance applied to randomly assigned experimental units

Question 11

Principles of experimental designs

Answer 11

control, randomize, replicate, block

Question 12

Statistically significant

Answer 12

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 statistically significant

Question 13

Control group

Answer 13

the experimental units assigned to a baseline treatment level, typically either the default treatment, or a null, placebo treatment

Question 14

Blinding

Answer 14

any individual associated with an experiment who is not aware of how subjects have been allocated to treatment groups

Question 15

Single blind

Answer 15

when every individual in either of these classes is blinded

Question 16

Double blind

Answer 16

when everyone in both classes is blinded

Question 17

Placebo

Answer 17

a treatment to have no affect administered so that all the groups experience the same conditions

Question 18

Placebo effect

Answer 18

the tendency of many human subjects to show a response even when administered a placebo

Question 19

Blocking

Answer 19

when groups of experimental units are similar, it is often a good idea to gather them together into blocks

Question 20

Matching

Answer 20

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 variables of interest

Question 21

Designs

Answer 21

in a completely randomized design, all experimental units have an equal chance of receiving any treatment

Question 22

Confounding

Answer 22

when the levels of one factor are associated with the levels of another factor in such a way that their affects cannot be separated