Chapter 2

Question 1

Define observational study.

Answer 1

If the investigator observes characteristics of a subset of the members of one or more existing populations.

Question 2

What is the goal of an observational study?

Answer 2

To draw conclusions about the corresponding population or about differences between two or more populations.

Question 3

Define experiment

Answer 3

When an investigator observes how a response variable behaves when the researcher manipulates one or more of explanatory variables.

Question 4

What is the goal of an experiment?

Answer 4

To determine the effect of the manipulated factors on the response variable.

Question 5

What conclusions is it impossible to draw from an observational study?

Answer 5

Cause and effect conclusions

Question 6

Define confounding variable.

Answer 6

A variable that is both related to both group membership and the response variable of interest in a research study.

Question 7

What is bias in sampling?

Answer 7

The tendency for samples to differ from the corresponding population in some systematic way.

Question 8

What are the most common types of bias?

Answer 8

Selection bias, measurement or response bias, and no response bias.

Question 9

When does selection bias occur?

Answer 9

When the sample is selected and excludes part of the population of interest.

Question 10

When does measurement or response bias occur?

Answer 10

When the method of observation tends to produce values that systematically differ from the true value in some way.

Question 11

When does no response bias occur?

Answer 11

When responses are not obtained from all individuals selected for inclusion in the sample.

Question 12

Define Simple Random Sample.

Answer 12

Every individual in every subset of the population has an equal chance of getting picked.

Question 13

Give an example of SRS.

Answer 13

Putting the names of everyone in a class in a hat. 
Could result with all boys or all girls.

Question 14

Define sampling frame.

Answer 14

A list of the objects or individuals in the population.

Question 15

What is sampling with replacement?

Answer 15

When each item that is picked is put back into the population with a chance of being picked again.

Question 16

What is sampling without replacement?

Answer 16

When an item selected isn’t placed back into the population.

Question 17

Define stratified sampling.

Answer 17

The population is divided into a set of no overlapping subgroups.

Question 18

Define strata.

Answer 18

Subgroups

Question 19

Define cluster.

Answer 19

Non overlapping subgroups

Question 20

Define cluster sampling.

Answer 20

When the tester divides the population into subgroups, then randomly chooses a subgroup and tests all the subjects in that subgroup.

Question 21

Define systematic sampling.

Answer 21

Picking every nth number from a list.

Question 22

What is convenience sampling?

Answer 22

When you use an easily available or convenient group to form a sample.

Question 23

Define voluntary sampling.

Answer 23

When individuals volunteer to be in the test.

Question 24

Define experiment.

Answer 24

A planned intervention undertaken t observe the effects of one or more variables. Must include a treatment.

Question 25

Define design.

Answer 25

The overall plan for conducting an experiment.

Question 26

Define extraneous factor.

Answer 26

A factor that’s not of interest in the current study but is thought to effect the response.

Question 27

Define blocking.

Answer 27

Groups that are similar with respect to the blocking factors.

Question 28

Define confounded factors.

Answer 28

When the effect of two factors can’t be distinguished in the response.

Question 29

Define randomization.

Answer 29

Random assignment to experiment groups

Question 30

Define replication.

Answer 30

The design strategy of making multiple observations for each experimental condition.

Question 31

Define direct control.

Answer 31

Holding extraneous factors constant so that this effects are not confounded with those of the experimental conditions.

Question 32

Define placebo.

Answer 32

Something that is identical to the treatment, but not the treatment.
Ex.
A sugar pill instead of a drug.

Question 33

Define double blind

Answer 33

When neither the subjects nor the individuals who measure the response know which group is teeatment.

Question 34

Define single blind.

Answer 34

When only the subjects don’t know of they are in the treatment group or not.

Question 35

Define experimental unit.

Answer 35

The smallest unit to which the treatment can be applied.

Question 36

Define survey.

Answer 36

A voluntary encounter between strangers where an interviewer asks the interviewee questions.

Question 37

What are the respondent’s tasks?

Answer 37

• Comprehension
• Retrieval from memory
• Reporting the response