Chapter 5: Experiments and Observational Studies

Question 1

explanatory variable

Answer 1

one that attempts to explain or is purported to cause (at least partially) differences in a response variable (sometimes called an outcome variable).

Question 2

treatment

Answer 2

one or a combination of categories of the explanatory variable(s) assigned by the experimenter.

Question 3

randomized experiment

Answer 3

we create differences in the explanatory variable

and then examine the results.

Question 4

observational study

Answer 4

observes differences in the explanatory variable and then notice whether these are related to differences in the response variable.

Question 5

interactions

Answer 5

An interaction occurs when the effect of one explanatory variable on the response variable depends on what’s happening with another explanatory variable.

Question 6

experimental units

Answer 6

the smallest basic objects to which we can assign different treatments in a randomized experiment

Question 7

observational units

Answer 7

the objects or people measured in any study.

Question 8

participants/ subjects

Answer 8

commonly used when the observational units are people.

Question 9

volunteers

Answer 9

the participants in studies

Question 10

control groups

Answer 10

groups which are handled identically to the treatment group(s) in all respects, except that they don’t receive the active treatment.

Question 11

placebo

Answer 11

A placebo looks like the real drug but has no active ingredients.

Question 12

placebo effect

Answer 12

the effect where the placebo produces the same side effects as the drug for the mere fact that the patient taking the drug thinks that they are receiving an actual treatment

Question 13

double-blind procedure/ experiment

Answer 13

A double-blind experiment is one in which neither the participant nor the researcher taking the measurements knows who had which treatment.

Question 14

single-blind procedure/ experiment

Answer 14

A single-blind experiment is one in which only one of the two, the participant or the researcher taking the measurements, knows which treatment the participant was
assigned.

Question 15

matched-pair designs

Answer 15

Experimental designs that use either two matched individuals or the same individual to receive each of two treatments

Question 16

randomized block design/ block design

Answer 16

An extension of the matched-pair design to three or more treatments is called a randomized block design, or sometimes simply a block design.

Question 17

repeated-measures designs

Answer 17

designs in which the same participants are measured repeatedly

Question 18

ecological validity

Answer 18

the variables have been removed from their natural setting and are measured in the laboratory or in some other artificial setting. Thus, the results do not accurately reflect the impact of the variables in the real world or in everyday life.

Question 19

case-control study

Answer 19

In such a study, “cases” who have a particular attribute or condition are compared with “controls” who do not.

Question 20

retrospective studies

Answer 20

observational studies in which participants are asked to recall past events

Question 21

prospective studies

Answer 21

observational studies in which participants are followed into the future and events are recorded