Chapter 4.3

Question 1

Observational study

Answer 1

a study in which data is collected without imposing any treatments, cannot show cause

Question 2

Retrospective study

Answer 2

examines existing data on individuals

Question 3

Prospective study

Answer 3

follows individuals to gather future data

Question 4

Experiments

Answer 4

a study in which treatment is imposed on subjects, can show cause and effect

Question 5

Experimental units (subjects)

Answer 5

the individuals that are assigned to different treatments

Question 6

Explanatory variable

Answer 6

the variable that is purposefully changed/manipulated

Question 7

Treatments

Answer 7

the different levels of the explanatory variable (dosage, placebo, etc.), what exactly is imposed on the subjects

Question 8

Response variable

Answer 8

the measured experiment outcome that is compared between the treatment groups

Question 9

4 principles of experimental design

Answer 9

comparison, random assignment, replication, control for confounding variables

Question 10

comparison

Answer 10

at least two treatment groups to compare effects between

Question 11

random assignment

Answer 11

good way to avoid groups that have systematic differences between them, diverse groups

Question 12

replication

Answer 12

ensure that each group in the experiment has multiple subjects, ensures results are not coincidental

Question 13

control (for confounding variables)

Answer 13

making sure that only the explanatory variable is producing the observed effect on the response variable

Question 14

confounding variables

Answer 14

anything that could influence the response variable other than the explanatory variable

Question 15

completely randomized design

Answer 15

an experimental design in which subjects are assigned to treatments completely at random

Question 16

Randomized block design

Answer 16

subjects are first blocked/grouped by a similar trait that may affect response. The units from each block are randomly assigned to treatment

Question 17

matched pairs design

Answer 17

a type of randomized blocked design in which each block is composed of two similar individuals (ex twins), can be paired with yourself in which case order of treatments is randomly assigned

Question 18

placebo

Answer 18

an inactive treatment

Question 19

placebo effect

Answer 19

when subjects’ belief of receiving an active treatment leads to a measured response, even though the treatment is actually inactive

Question 20

single blind study

Answer 20

either the subjects or the researchers are unaware of who receives which treatment

Question 21

double blind study

Answer 21

both the subjects and the researchers are unaware of who receives which treatment

Question 22

generalization

Answer 22

using study results to make inferences about a larger population

Question 23

If neither random sampling nor random assignment occurred…

Answer 23

(case study, anecdotal study) then we cannot generalize or determine cause and effect, may be a good starting point to decide if further research is worth it

Question 24

If random sampling occurred but not random assignment…

Answer 24

(observational study) then we we can generalize the results from the study to the population that we sampled from

Question 25

If random assignment occurred but not random sampling…

Answer 25

(experiment) then we can determine the cause and effect relationship between the explanatory and response variables

Question 26

If both random sampling and random assignment occurred…

Answer 26

(experiment with random sampling) then we can generalize the cause and effect relationship to the population we sampled from