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2801 > W2 S16 > Flashcards

W2 S16 Flashcards

(47 cards)

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1
Q

Target population

A

people you want your results to apply to
ex, everyone in Canada

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2
Q

Source population or Sampling frame

A

People from whom the population is selected
-population where your study subjects are drawn
ex, everyone on Canadian Electrical role

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3
Q

Sample

A

people approached to take part in the survey
ex, random sample of those listed

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4
Q

Study population

A

people who actually took part in the survey
ex, those who agree to take part

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5
Q

What is Probability Sampling?

A

It involves using selection techniques wherein the probability of each sampling unit is know

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6
Q

What are the 5 methods of Probability sampling?

A
  1. Simple random sampling
    -ex, picking out of hat
  2. Systemic Sampling
    -ex, picking every 3rd person
  3. Stratified random sampling:
    -ex, random sampling from distinct groups
    4.Cluster sampling:
    -ex,(natural clusters rather than individual units are selected
  4. Multistage sampling:
    ex,( primary sample units are selected
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7
Q
  1. Simple random sampling:
A
  • number population and randomly choose numbers that come out of random number generator
    -ex, picking number out of hat
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8
Q
  1. Systematic Sampling
A

-usually, a random start
-the ORDER of population in the sample frame should be RANDOM (not by age or cities for example)

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9
Q
  1. Stratified Sampling
A

Random samples from distinct groups
–geography (urban, rural, suburban
–sex (male, female, other)

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10
Q

4.Cluster Sampling

A

-Natural clusters (schools, neighbourhoods) rather than individual units are selected
-observation are made on ALL units within a cluster
-cluster sampling of schools
—-all eligable children within each school included
1) Four out of 10 clusters are randomly selected
2) All within the selected clusters are recruited

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11
Q
  1. Multistage Sampling
A
  • primary sampling units are selected (e.g) municipalities)
    -secondary units selected within primary units (e.g. individuals)
    -may have more levels
    —–secondary units: city blocks
    —–tertiary units: individuals
    1) Five out of 10 clusters are randomly selected
    2) within the selected clusters participated are (again) randomly sampled
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12
Q

Non-probability sample
Convenience Sample:

A

Selection from A non-probability based source population due to ease of access to those individuals, schools, workplaces, organizations, or communities
-use with caution
-often systematically different from the target and source populations they are intended to represent

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13
Q

Non-probability sample
Purposive sampling:
(think of purple)

A
  • recruitment of the participants for a QUALITATIVE study based on the special insights they can provide
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14
Q

Key informants

A

are individuals selected to participate in a qualitative study because they have expertise relevant to the study questions

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15
Q

What are the errors associated with sampling?
-does the sample represent the ____ population?
External validity -
Sampling bias-
selection bias-

A
  • does the sample represent the target population
  • external validity:
    the ability of its results to be generalized to the entire population
    -sampling bias:
    error that systematically skews results in a certain direction.
    -Selection bias
    is a kind of error that occurs when the researcher decides who is going to be studied.
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15
Q

n

A

n

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16
Q

Berkson’s bias

A

can occur when cases and controls for a study are recruited from hospitals and therefore are more likely than the general population to have comorbid conditions
-choose more vulnerable people for study

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17
Q

Health worker bias

A

can occur when participants are recruited from occupational populations and therefore are systematically healthier than the general population
-choose healthier people for study

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18
Q

Exclusion bias

Study These Flashcards
A

occurs when different eligibility criteria are applied to cases and controls, such as when controls with health conditions related to an exposure are excluded but cases with those comorbidities are not excluded

-For example, if patients died from toxic effects of an experimental treatment and were subsequently excluded from the trial analysis, perhaps as ‘early deaths’, the estimate of effect would be biased in favour of that experimental treatment.

19
Q

What are the ethical issues in sampling vulnerable populations?

Study These Flashcards
A

-those who might have limited ability to make an autonomous decision about volunteering to participate in a research study
–young children
–some individuals with serious health issues
–people in prison and some other socially marginalized populations
–limited ability to make an independent decision about volunteering because of other reasons
-should not be selected unless absolutely necessary
-at the same time, systematically EXCLUSION IS ALSO UNETHICAL
-THEIR HEALTH. issues should be studied
-extra consideration of the potential risks of research to participants (stricter ethical considerations)
-CIHR core ethics modules

20
Q

Sample Size and Power
Why is sample size important?

Study These Flashcards
A
  • we want to recruit just the RIGHT NUMBER of participants
    –recruiting too many participants wastes resources
    –recruiting too few participants makes the study invalid
    -The desired sample size (the number of observations in a data set) for a quantitative study is based on statistical estimations about how many data points are required in order to answer the study question with a SPECIFIED LEVEL OF CERTAINTY
21
Q

Sample size can be calculated based on…

Study These Flashcards
A
  • the effect estimate of exposure on the outcome
    -the amount of error(s) we can accept
    -variation in the population
22
Q

Type 1(a) and 2(b) Errors

Study These Flashcards
A

-null means there is no exposure/outcome association
Type 1 error: false postive
Type 2 error: false negative

23
Q

Type 1 error (a)
false positive

Study These Flashcards
A

occurs when a study population yields A STATISTICALLY-SIGNIFICANT test result even though a significant difference or association DOES NOT ACTUALLY EXIST in the source population
ex, telling a guy hes pregnant

24
Type 2 error (b) false negative
occurs when a statistical test or data from research find NO SIGNIFICANT RESULT even though a significant difference or ASSOCIATION ACTUALLY EXISTS in the source population -ex, telling mom she is not pregnant but notice huge baby kicking
25
Amount of random a and b errors is a function of sample size
(1-B) is usually referred as the POWER of the study, i.e. how much study is ABLE to detect a TRUE RELATIONSHIP, can be calculated post hoc (after the study is completed )
26
The next step in the Reseach process is to collect data...sample the population and measure the variables In the example is household size a risk factor for covid 19 london.... you should be doing what when collection data specifically when measuring variables
1. Surveying home 2. Use of admin data
27
Data collection in Health - Often (NOT ALWAYS) is conduced by interviewing (either self or by an interviewers) paricipants via questionnaires or survey instruments What are other methods?
-Direct measurement of physical functioning (measurement of height, weight, blood pressure) -blood work (measurement of hormones, sugar) -sampling other tissues -imaging (x-ray, CT scan, MRI)
28
Interview is...
...the process of verbally asking a participant questions and recording that person's responses -trained interviewers record the responses, and they can ensure the accuracy and completeness of each questionarre -interviews may require major time commitments from study personnel
29
self-administered survey
is a questionnaire form that participants complete by themselves, using either a papaer-and pencil version or online
30
In-depth interview for qualitative studies Spending 1 or 2 hours interviewing A KEY informant (not smapled) using open-ended questions What is a semi-structured interview? start w OEQ What is Probing?
-A semi-structured interview is where the interviewer starts with a list of open-ended questions that will be asked of each participant, but these questions or lists of topics are merely starting points for eliciting responses from participants Probing is an interviewing technique that prompts an interviewee to provide a more complete specific response (prob be more specific with your response) -interviews can also record their observations of the body language and other nonverbal communication conveyed by interviewees
31
Interview -What is it? -What are examples? What are the pros and cons?
-A member of the research team asks questions of participants and records their responses - examples include in-person (face-to-face interviews, telephone interviews) -Pros: we can TRAIN interviewers to ensure the accuracy and completeness of each questionnaire -Cons: may require major time commitments, expensive
32
Self-administered survey -What is it? -What are examples? What are the pros and cons?
- participants are provided with a set of questions and record their own answers -examples include: completion in presence of researchers, mail, email/internet-based survey -Pros: cost and time-efficient possibly of approaching a large number of participants the best way to get honest answers to sensitive questions Cons: Problematic for low literacy populations, and those who have limited internet access or be unfamiliar with computers
33
Training interviewers
Standard protocols will be followed to ensure THE INTERVIEW PROCESS IS THE SAME for all study participants -all interviewers should undergo role-specific training and have an opportunity to practice their interview skills, pilot testing, quality control to avoid
34
Interviewer bias
occurs when interviewers systematically question cases and controls or exposed and unexposed members of a study population differently, such as probing only individuals they believe to have the disease or exposure of interest for more information
35
Uniformity
is easiest to accomplish when all interviewers are provided with the tools they need to follow a standardized set of procedures
36
Questionnaire
a series of questions used as a TOOL for SYSTEMATICALLY GATHERING DATA from study participants
37
Systematically gathering data Focused and specific content
1) List the topics that the survey instrument must cover Theoretical frameworks can inform the diversity of questions that may be relevant to include in the survey instrument 2) The firs set of questionnaire items typically are ones that enable the researcher to confirm that participants meet the eligibility criteria fir the study, exclude ineligible people 3) Several questions may be required in order to accurately assign participants to key exposure and disease categories Recall PICOT
38
Closed-ended questions
allow a limited number of possible responses -date and time questions -numeric questions -categorical -----ranked (ordinal) categorical answers have an inherent order ------ unordered (nominal) categorical answers do not have any built-in order -paired comparisons
39
open-ended questions (also called free response questions) .......
allow an unlimited number of possible responses
40
Practical Considerations 1) Order of questions
-it is better to start with easy or at least general questions before moving to more difficult or sensitive questions -it is often best to group similar questions with similar response types, so that they are asked consecutively
41
Practical Considerations 2) Getting the correct answer
- sometimes it is better to mix up questions to prevent HABITUATION, an error that occurs when participants becomes so accustomed to giving particular response (like "agree..agree.....agree...") that they continue to reply with the same response even when that does not match their true perspectives -survey developers must carefully consider how previous questions could taint the answers to later ones
42
Practical Considerations 3) Data recording methods
- Option 1: Record the responses on paper and to enter or scan them into a computer later -may be required for the collection of data from a large number of particpants at one time data entry is often a very time-consuming and costly process (manually) -Option 2. Have interviewers or participants enter responses directly into a database - eliminates the need for later data entry -some population are uncomfortable with computer technology -automatic
43
Practical Considerations 5) Back translation
-in international studies it is crucial to have HARMONIZES surveys -one person translates the questionnaire from the orginal language to a new language, then a second person then translates the survey insrument in the new langauge BACK into original langauge - a comparison of the original version with the back-translated version will reveal where the second-langauge translation does not match the intended meaning of the orginal version
44
Practical consideration Pilot testing
- a small-scale preliminary study conducted to evaluate the FEASIBILITY of a full-scle research project -the survey instrument is revised based on the observations
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4) Layout and formatting
-paper-based and electronic survey pages should be carefully checked for grammatical errors, misspellings, gaps in logic,unclear instructions, readability, and other organizational issues - computer-based data entry programs allow a researcher to force participants to provide an answer to selected questions, but forcing a person who does not want to provide an answer to one question may encourage the person to quit the survey and leave all subsequent items unanswered What would you do when you see a sensitive question that you are forced to answer? Skip logic: codes can automatically hide irrelevant questions from participants based on their responses to filer questions, e.g. after a No answer to ‘are you employed? All questions about satisfaction with the job won’t appear

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