Week Three Flashcards

You may prefer our related Brainscape-certified flashcards:
1
Q

What is a sampling frame and a sampling unit?

A

Sampling frame: the list from which the elements of the population are selected

Sampling unit: any single unit sampled from the population, primary sampling units - entitles selected in the first stage of the sample, secondary sample units - entities selected in the second stage of the sample if there is one

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

What are the two types of generalisability

A

Sample generalisability: ability to generalise from a subset of a larger population (I.e. Sample) to that population itself. This often occurs through inferential statistics

Cross- population generalisability (external validity): ability to generalise from the findings about one group, population, or setting to other groups, populations or settings

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

What is a sampling error

A

Any difference between the characteristics of a sample and the characteristics of the population from which it was drawn

The larger the sampling error, the less representative the sample is of the population

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

What is probability

A

Sample methods that allow us to know in advance how likely it is that any element of a population will be selected

Random selection: everyone in the population has a know / equal chance to be picked

Non-probability: sample methods in which the likelihood of selection is not know in advance

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

What does probability sampling do

A

Allows researchers to select study subjects to be statistically representative of population they want to learn about (generalisability)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

What is simple random sampling?

A

Identifies cases strictly on the basis of chance eg random number tables

Typically every subject has equal probability of being selected

CANNOT do this without a sampling frame that contains every element of the population

Can be done with or without replacement sampling

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

What is replacement sampling

A

Each element is returned to the sampling frame from which it is selected so that it may be sampled again

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

What is systematic random sampling?

A

The first element is selected randomly from a list, and then every nth element thereafter is selected

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

What are the three steps of systematic random sampling?

A

Calculate sampling interval: the total number of cases in pop is divided by the number of cases required in the sample

Identify the first case to be selected: a number within the sampling interval is randomly selected and used to select the first case

Selection of subsequent cases: every nth case is selected, wherein is the sampling interval

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

What is stratified random sampling

A

Uses information known about key characteristics of the population prior to sampling to make the process more efficient

Often used to ensure that subjects who have a Rare or uncommon characteristics are adequately represented in the sample

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

What are the two steps of stratified random sampling?

A
  1. Distinguish all elements in the populations (I.e. In the sampling frame) according to their value on some relevant characteristic.
    - that characteristic forms the sampling strata
    - each element must belong to one and only one stratum
  2. Sample elements randomly from within each strata
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

What is proportionate and disproportionate stratified sampling

A

Proportionate ratified sampling: every group is equally proportional to its size in the population

Disproportionate stratified sampling: proportionate of each group is unite nationally varied from population - useful to include small or underrepresented groups

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

What is multistage cluster sampling

A

Sampling in which elements are selected in two or more stages

  1. Clusters: preexisting groups of elements in a population - a random sample of clusters is selected
  2. Within clusters: within each cluster a random sample of elements is selected
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

What is non probability sampling

A

Each member of population is an unknown probability of being selected

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

What are the four types of non probability sampling

A

Availability or convenience

Snowball

Quota

Purposive/judgment

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

What is convenience sampling

A

Elements are selected because they are available or easy to find

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
17
Q

What is quota sampling

A

Elements are selected to ensure that the sample represents certain characteristics of the population

Similar to stratified probability sampling but generally less rigorous and precise in selection procedures

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
18
Q

What is purposive sampling

A

Each sample element is selected for a purpose. Usually because if the unique position of the sample elements

May involve studying the entire population of some limited group or a subset of a population

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
19
Q

What is snowball sampling

A

Sample elements are selected as they are identified by successive informants

Useful for hard to reach populations in which members are interconnected

20
Q

What is random sampling error

A

Refers to the difference between a sample statistic and the true value in the population due solely to chance

21
Q

What is sampling distribution

A

Statisticians estimate the probability that a sampling result is representative of a population using this

Estimates the margin of error and confidence interval around the sample statistic

Sampling distribution for many statistics is a normal or bell shape

22
Q

What is systematic sampling error

A

Refers to differences between the sample and population due to some problem with the sampling method

23
Q

What is ecological fallacy and reductionism

A

Eco: a researcher draws conclusions about individual level processes from group level data

Reductionism: a researcher draws conclusions about group level processes from individual level data

24
Q

What are the two types of causal explanations

A

Quantitative (nomothetic)

Qualitative (idiographic)

25
Q

What is nomothetic causal explanation?

A

Quantitative

Involved the belief that variations in an independent variable will be followed by variation in the dependent variable, when all other things are equal (ceteris pariaus)

The value of cases on the dependent variable differs from what their values would have been in the absence of variation in the indecent variable (counterfactual)

26
Q

What is the idiographic causal explanation

A

When a series of concrete events, thoughts or actions result in a particular event or individual outcome

Includes statements of inital conditions and then relates a series of events st different times that led to outcome

Explanation is concerned w context and deterministic

Focus on time order and causal mechanism

27
Q

What is the five criteria for causation in research design

A

Empirical association (required)

Time order (required)

Nonspuriousness (required)

Mechanism

Context

28
Q

Why is empirical association

A

Variation in one variable is related to variation in another

Relationship must be observed - cannot be assumed or believed

The independent variable and the dependent variable must vary together

Same direction of variation - positive associations
Opposite direction - negative associations

29
Q

What is time order

A

The change in the independent variable must occur before the change in the dependent variable

30
Q

What is nonspuriousness

A

A relationship between two variables that is not due to variation in a third variable

When this third variable (an extraneous variable) cause the variation, it creates a spurious relationship between the independent and dependent variable

31
Q

What is causal mechanism

A

Process that creates the connection between variation in an independent variable and the variation in the dependent variable it is hypothesised to cause it

32
Q

What are the two experimental research designs and two non-experimental?

A

Experimental:

True experiments

Quasi experiments

Non experimental

Cross-sectional

Longitudinal

33
Q

What are the three requirements of true experiments

A
  1. An experimental group that is reviewing condition and one control group that is not
  2. Must have random group assignment
  3. Must have assessment of change (pre and post) in both groups both change is elected

Research design is quasi-experiment when all but one requirements are met

34
Q

Explain cross sectional designs

A

Observations are made at one time point

Independent variable is fixed at some point prior to the variation in the dependent variable

You believe respondents can give you reliable reports of what happened to them or what they thought at some earlier time

Measures are based on accurate records that contain information in cases in earlier periods

You know that the value of the dependent variable was similar for all cases prior to the treatment

35
Q

What are the three types of longitudinal design

A

Repeated cross sectional design

Fixed sample panel designs

Event based designs

36
Q

What is repeated cross sectional design

A

Trend

Data is collected at two or more points in time from different samples of the same population

Appropriate design when the goal is to determine whether a population has changed over time

37
Q

What is fixed sample panel design

A

Data are collected from the same individuals (the panel) at two or more points in time

Issues: cost and subject attrition - leaving

38
Q

What is event design

A

Event or cohort based design

Data are collected at two or more point in time from individuals in a cohort

Types of cohorts: birth, seniority, school etc

Can be repeated cross sectional design or a type of panel design

39
Q

What is individual and aggregate matching

A

Two selection methods for quasi experimental

Individual: individual cases in the treatment groups are matched with similar individuals in the control group

Aggregate: using group level data, the treatment group is matched to similar control group

40
Q

What is internal validity and it’s five sources

A

Ability to yield valid conclusions is determined by comparability of experimental and control groups.

Sources:

Selection bus

Endogenous change

External events

Contamination

Treatment misidentification

41
Q

What is selection bias

A

Treatment and comparison group are different at beginning or end of study - one group has more experience, education etc

Differential attrition is one type of selection bias: groups become different because for various reasons subjects are more likely to drop out of groups

A pretest helps determine whether selection bias exists and controls for it

42
Q

What is endogenous change?

A

Occurs when natural developments in the subjects, independent of the experimental treatment, account for some or all of the observed changes between pretest and post-tests

Three specific threats:
- testing: pre-test influenced post-test scored because subject learn something earlier and react different

Maturation: part of natural maturational experience, subjects respond differently on the post-test than they did in the pre- test

Regression to the mean: subjects experience cyclical or episodic changes that result in different posttest scores

43
Q

What is contamination

A

Occurs when the control group is in some way affected by or affects the treatment groups

Two types:

Compensatory rivalry: control group member works harder to make up for not having treatment or intervention

Demoralisation: control group member feels left out and becomes worse than he/she would have been without study

44
Q

What is treatment misidentification

A

Occurs when the treatment itself does not cause the outcome but does cause some intervening process the researchers is not aware of

Sources:
The halo effect: staff too excited toward certain group

Placebo effect: improve because of expectation not treatment

Hawthorne effect: subjects may change because more attention is being paid to them

45
Q

What is external validity

A

The application of a treatment across subgroups within an experiment and/or across different populations, times or settings

Sample generalisability

46
Q

What is factorial survey design

A

Can increase generalisability

Embed the features of true experiments into a survey design in order to maximise generalisability

Randomly selected subsets of respondents are asked different questions or asked to respond to different vignettes

Allows researchers to determine the causal effect of the variables represented by these differences

47
Q

What is the Institutional review board?

A

Committee that review research proposals to ensure that research is abiding by ethical principles

Required for every institution that seeks federal funding for biomedical or behavioural research on human subjects