Chapter 4 - Designing Studies Flashcards Preview

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Flashcards in Chapter 4 - Designing Studies Deck (44)
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0
Q

collects data from every individual in the population

A

census

1
Q

statistical study of the entire group of individuals we want information about

A

population

2
Q

subset of individuals in the population from which we actually collect data

A

sample

3
Q
  • state exactly what population we want to describe

- state exactly what we want to measure

A

sample survey

4
Q

choosing individuals from the population who are easy to reach results in a ____.
-often produces unrepresentative data & is bias

A

convenience sample

5
Q

using a method that favors some outcomes over others

A

bias

6
Q

if you’re asked to describe how the design of a study leads to bias, you’re expected to do two things:

A

1) identify a problem with the design

2) explain how this problem would lead to an underestimate or overestimate

7
Q

another term for voluntary response samples

A

self selected samples

8
Q
  • consists of people who choose themselves by responding to a general invitation
  • people who feel strongly about an issue
  • most responders share same opinion leading to bias
A

voluntary response sample

usually not representative of a larger population of interest

9
Q

-uses a chance process to determine which members of a population are included in the sample
ex- pulling names out of a hat

A

random sampling

10
Q

-resulting sample of a random sampling method
-size n is chosen in a way which every group of n individuals in the population has an equal chance to be selected as the sample
ex- drawing 20 slips out of a hat containing 200 identical slips

A

simple random sample (srs)

11
Q

stratified random sample and strata

A
  • classifying population into groups of similar individuals (strata)
  • choosing separate SRS in each stratum and combine these SRSs to form the sample
  • works best when the individuals in each stratum are similar with respect to what is being measured
12
Q

cluster sample

A
  • classify the population into groups of individuals that are located near each other (clusters)
  • choose an SRS of the clusters
13
Q

list of individuals from which a sample will be drawn

A

sampling frame

14
Q

bad sampling methods

A

convenience sampling or voluntary response

15
Q

occurs when some members of the population cannot be chosen in a sample;
ex- a sample survey of households will not account for homeless people

A

under coverage

16
Q
  • occurs when an individuals chosen for the sample can’t be contacted or refuses to participate
  • can only occur after sample has been selected
A

non response

17
Q

-systematic pattern of inaccurate answers in a survey

ex- people lying about age, income, or drug use

A

response bias

18
Q

confusing or leading questions that can lead to strong bias

A

wording of questions

19
Q
  • observes individuals and measures variables of interest but does not attempt to influence the responses
  • used to describe group or situation, compare groups, or examine relationships between variables
A

observational study

20
Q
  • deliberately imposes some treatment on individuals to measure their responses
  • only true source of cause and effect
A

experiment

21
Q

when two independent variables cannot be distinguished from each other as what is really affecting the dependent variable

A

confounding

22
Q

specific condition applied to individuals in an experiment

A

treatment

23
Q

experimental units

A

smallest collection of individuals to which treatments are applied

24
Q

factors

A

explanatory variables in an experiment

25
Q

level

A

each treatment that is form by combining a specific value of each of the factors

26
Q

random assignment

A

experimental units are assigned to treatments using a chance process

27
Q

replication

A

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

28
Q

principles of experimental design

A
  1. comparison
  2. random assignment
  3. control
  4. replication
29
Q

control

A
  • prevent confounding

- reduce variability in response variable

30
Q

experimental units are assigned to the treatments completely by chance

A

completely randomized design

31
Q

provides baseline for comparing effects of the other treatments

A

control group

32
Q

placebo effect

A

response to a dummy treatment

33
Q

double blind experiment

A

neither subjects or researcher knows which is the control group and which receives treatment

34
Q

single blind experiment

A

researcher knows difference between the two groups but participants are unaware if they are receiving treatment or placebo

35
Q

observed effect so large that it would rarely occur by chance

A

statistically significant

does imply causation

36
Q

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

A

block

37
Q

randomized block design

A
  • random assignment of experimental units to treatments is carried out separately within each block
  • allows us to account for variation in response
38
Q

matched pairs design

A
  • type of randomized block design for comparing two treatments
  • create blocks by matching pairs of similar experimental units
39
Q

random selection of individuals allows inference about the ____

A

population

40
Q

random assignment of individuals to groups permits inference about ____

A

cause and effect

41
Q

institutional review board

A

charged with protecting safety and we being of subjects

42
Q

basic data ethics

A
  • institutional review board
  • informed consent
  • confidentiality
43
Q

lack of realism

A

can prevent us from generalizing results