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POPM*3250 > Unit 6-7 > Flashcards

Unit 6-7 Flashcards

1
Q

A study that does not intervene or change anything in the person’s life is called….

A

observational study

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2
Q

What type of study is an observational study?

A

analytical study

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3
Q

What are 2 types of analytical studies?

A

observational and experimental

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4
Q

What are 3 types of observational studies?

A
  • cross-sectional
  • case-control
  • cohort
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5
Q

What are 3 types of descriptive studies?

A
  • case reports
  • case series
  • descriptive surveys
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6
Q

What are the major differences between descriptive and analytical studies?

A

Descriptive:

  • what?
  • collects info
  • does not establish association between cause and effect

Analytical:

  • why?
  • investigate the reason for disease/death/even to control the problem
  • compares between groups
  • association between E and O
  • good for testing hypotheses
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7
Q

When would an observational study be better than experimental study?

A
  • intervention is unethical
  • intervention is expensive
  • exposure is complex/hard to control
  • not practical to administer exposure
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8
Q

How are cross sectional study subjects selected?

A

chosen without regard to exposure or outcome status

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9
Q

How are case control study subjects selected?

A

chosen based on outcome status

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10
Q

How are cohort study subjects selected?

A

chosen based on exposure status

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11
Q

What are 5 main steps in cross-sectional studies?

A
  • randomly sample from source population
  • take measurements of individuals all at one point of time
  • classify E+/E-
  • classify O+/O-
  • compare prevalence or odds of disease in E+ or E- groups
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12
Q

What are some advantages of cross-sectional studies?

A
  • can determine prevalence of E and O
  • fast and inexpensive
  • less bias than case control
  • study permanent factors
  • assess association between multiple E and multiple O
  • random sampling, estimates all measures of association and effect but no true rates
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13
Q

What are disadvantages of cross- sectional studies?

A
  • not good for rare E or rare O (cuz random sampling)
  • prone to major forms of bias if not considered (selection, information, confounding)
  • measures prevalence, but not incidence (because it takes a snapshot of one moment in time)
  • temporality (prevalence, not incidence, did E actually come before O?)
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14
Q

What are 3 major steps for case-control studies?

A
  • purposively sample individuals from population of interest O+ and O-
  • classify each individual on basis of E+ or E-
  • compare proportion of O+ subjects that are E+ vs E-
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15
Q

What are some advantages of case-control studies?

A
  • rare disease (outcome), not rare exposure
  • to investigate source of an outbreak
  • good for identifying multiple risk factors (E) for one disease (unknown cause)
  • fast and inexpensive because retrospective (historical)
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16
Q

What are disadvantages of case control studies?

A
  • cannot calculate incidence or prevalence (chose on the basis of disease/not diseased
  • examines only one outcome
  • MOST prone to bias (looking back in time to obtain data)
  • temporal relationship are issue in prevalent cases (new and old)
  • control selection may be difficult to select
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17
Q

What is a primary study base?

A

population which cases arise that can be easily defined
good sense of where population of all cases are coming from
(i.e. a daycare, a farm)
(for case control studies - selecting case population)

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18
Q

What is a secondary study base?

A

population of potential study subjects that is one or more steps removed from primary study population
- wide range of backgrounds/difficult to define
(for case control studies - selecting case population)

19
Q

How are cohort study subjects selected?

A

on the basis of exposure status

20
Q

What do cohort studies measure?

A

incidence of disease (of new cases)

21
Q

What are advantages of cohort studies?

A
  • good for RARE exposures
  • several outcomes
  • temporal sequence established (prospective)
  • attain incidence data
  • can measure all association and effect
22
Q

What are disadvantages of cohort studies?

A
  • expensive
  • time consuming
  • bad for rare outcomes
  • susceptible to loss to follow up
23
Q

What type of study cannot calculate relative risk?

A
  • case-control studies
24
Q

What type of study can calculate all measures of association and effect?

A

cohort studies

  • RR, OR, IRR
  • RD, APe, PAR, PAF
25
Q

What are 2 types of experimental studies?

A 
Lab experiments (clinical trials)
Field experiments (field trials)

these are intervention based studies

26
Q

What are advantages of lab experiments/randomized clinical trials?

A
  • highly controlled environment
  • confounding factors can be controlled
  • frequency and dose is set
27
Q

What are disadvantages of lab experiments/randomized clinical trials?

A
  • does not take into account of other factors /exposures in real-world scenarios
  • further study required (field study)
28
Q

What is a “challenge trial”

A
  • randomized clinical trial (lab experiments)

- study of subjects exposed to given exposure (i.e. a virus)

29
Q

What are advantages of field experiments/randomized field trials?

A
  • real world setting

- assess impact of various treatments in setting that can be applied to future individuals

30
Q

What are disadvantages of field experiments/randomized field trials?

A
  • logistically more difficult to carry out than clinical
  • involves healthy rather than diseased
  • may not develop disease o interest in short time frame
  • requires greater number of individuals to follow up for long time
31
Q

What is the main/major difference between clinical and field trials?

A

level of control

clinical trials have total control over challenge/exposure and environment
field trials aim to see if if agent/procedure reduces risk of naturally developing disease (therefore, little control)

32
Q

“Where the value of a treatment, old and new, is doubtful, there may be a higher moral obligation to test it critically than to continue to prescribe it year-in-year-out with the support merely of custom or wishful thinking”
“The question at issue, then, is whether it is proper to withhold from any patient a treatment that might, perhaps, give him benefit. The value of the treatment is, clearly, not proven; if it were, there would be no need for a trial. But, on the other hand, there must be some basis for it – whether it be from evidence obtained in test tubes, animals, or even in a few patients. There must be some basis to justify a trial at all.”
These are definitions of …

A

ethics

33
Q

A comparison group with no intervention in randomized trials is called…

A

Negative control

34
Q

A comparison group with an alternative intervention in randomized trials is called…

A

Positive control

35
Q

What are 3 ways to allocate individuals to treatment groups?

A
  • complete randomized design
  • randomized block design (like stratified - grouped first by factors of interest i.e. age, ethnicity)
  • cross-over design (each subject spends some time in treatment, and some time in control)
36
Q

If a study subject is aware that they are receiving treatment for specific outcome and report improvements if they don’t exist, this bias is called..

A

Wish bias

- tendency of patients or investigators to fit data of how they believe it should be

37
Q

When patients with certain characteristics are more likely to be admitted to hospital where their sample may be taken, this bias is called…

A

Differential admission bias

- the sample is unrepresentative of the target population

38
Q

The ability/inability of study subjects to correctly remember information that occurred in the past is what type of bias?

A

Recall bias

39
Q

Poor sensitivity or specificity of a test can lead to what type of bias?

A

Misclassification bias

- incorrectly classifying an individual

40
Q

Blinding is useful to eliminate what type of bias?

A

follow up bias

41
Q

What are 3 types of blinding?

A
  • single blinding (subject OR researcher blinded)
  • double blinding (subject AND researcher)
  • triple blinding (subject, researcher, data analysts blinded)
42
Q

What are REFLECT and CONSORT?

A

guidelines for randomized trials to improve level of reporting?

43
Q

What does REFLECT stand for?

A

reporting guidelines for randomized controlled trials for livestock and food safety
(animal subjects)

44
Q

What does consort stand for?

A

consolidated standards of reporting trials

human subjects

POPM*3250 (4 decks)

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