Class 6

Question 1

counterfactual

Answer 1

is what would have happened to the same
people exposed to a causal factor if they simultaneously
were not exposed to the causal factor

Question 2

effect

Answer 2

is the difference between what actually did

happen with the exposure and what would have happened without it

Question 3

counterfactual often used

Answer 3

control grp

Question 4

PICO question

Answer 4

pop
intervention
comparison
outcome

Question 5

Spurious association

Answer 5

variables are not causally related to each other,
yet it may be wrongly inferred that they are, due to either
coincidence or the presence of a certain third, unseen factor. ex: ebola vaccine, heart attack

Question 6

Indirect association

Answer 6

: variables are associated due to the presence of

another factor i.e. common factor (confounding variable).

Question 7

Direct ( causal ) association

Answer 7

• One to one causal association

* Multifactorial association

Question 8

Criteria for Causality (John Stuart Mill)

Answer 8

• Temporal : A cause must precede an effect in time
• Relationship There must be an empirical relationship between the presumed cause and the presumed effect (correlation)
• No confounders : The relationship cannot be explained as being caused by a third variable.

Question 9

Criteria for Causality: Hill

Answer 9

Strength: a strong association is more likely to be causal, linked to relative risk and not stats
Consistency: diff pop
Specificity: exposure is associated with a specific outcome only
Temporality: cause should precede the outcome + timing of exposure should be consistent with latency or incubation period
Gradient: when intensity of exposure increases, so does outcome
Plausibility: biologically plausible
Coherence: Not in conflict with what is known about the history and biology of the disease or its distribution in time and place
Exper evidence
Analogy

Question 10

Randomized Controlled Trial (RCT): Key Features

Answer 10

• Manipulation : The research does something to at least some participants there is an intervention
• Control : The researcher introduces controls over the research situation a comparator (counterfactual approximation)
• Randomization : The researcher assigns participants to a control or experimental condition on a random basis

Question 11

Control Group

Answer 11

1. An alternate intervention
2. Standard of care
3. Placebo
4. Different doses
5. Wait list or delayed treatment

Question 12

Randomization (Random Allocation)

Answer 12

•Prevent selection bias
•Equalize pre intervention attributes
(potential confounders)

Question 13

Types of randomization

Answer 13

• Complete randomization
• Simple randomization
• Stratified randomization: control for covariates

Question 14

Blinding

Answer 14

•Enhance objectivity
•Prevent expectation
bias
•Prevent
measurement bias

Question 15

Quasi

experimental design

Answer 15

•Lacks random assignment to an intervention or control group. Use of this type of
study occurs when it is not possible to randomize.
•A quasi experimental design identifies a comparison group that is as similar as
possible to the intervention or treatment group in terms of the baseline
characteristics.
•While potentially more practical than a randomized trial, this study design often
introduces bias when the experimental and control groups are not equivalent.
These types of studies are also sometimes referred to as “natural experiments.”

Question 16

Prospective cohort study

Answer 16

1.Identify participants based on exposure:
•Exposed or
•Unexposed (comparison group)
2.Assess outcomes based on prospective data collected

Question 17

Retrospective cohort study

Answer 17

•. In this type of study, both the exposure and the outcomes have already
occurred and data are collected retrospectively.
•Just as in a prospective cohort study, the investigator calculates and
compares rates of disease in the exposed and unexposed groups.

Question 18

Case

Control study

Answer 18

The investigator selects participants based on their disease status
(outcome) and then assesses previous exposures
1.Investigator enrolls those with the disease (outcome)
2.For a comparison group, the investigator then enrolls a group of
people without the disease (controls), representing the population
from which the cases originated
3.Investigators then compare previous exposures between the two
groups

Question 19

Cross-sectional

Answer 19

survey

Question 20

Incidence

Answer 20

The rate of new cases with a specified condition, calculated by dividing the
number of new cases by the number at risk of becoming a new case over a
given period of time (e.g. over the period of one year)
cohort study

Question 21

Prevalence

Answer 21

The proportion of a population having a specified condition at a given point in
time (e.g. a snapshot in time)
cross sectional survey

Question 22

Emergency Threshold for mortality

Answer 22

more than 1/ 10 000 per day

child: more than 2