Chapter 9: Measures of Effect Flashcards
What is an effect measure?
a quantity that measures the effect of a factor on the frequency or risk of a health outcome
- Attributable fractions: measure the fraction of cases due to a factor
- Absolute effects: risk and rate differences measure the amount of a factor adds to the risk or rate of a disease
- Relative effects: risk and rate ratios measure the amount by which a factor multiplies the risk or rate of disease
What is the difference measure of association?
a type of comparison. Used to compare the disease burden in 2 groups. A way to do that is to calculate the absolute difference in disease frequency
What is another name for difference measure of association?
Attributable risk
Risk difference?
the difference between the incidence rate of disease in an exposed group and a non exposed group
-RD= I(e)-I(ne)
Population risk difference?
a measure of the benefit to the population derived by modifying a risk factor
-I(p)total incidence rate= I(e)P(e)+ I(ne)P(ne)*
What is an etiologic fraction? Equation?*
defined as the proportion of the rate in the exposed group that is due to the exposure
-(I(e)-I(ne)/I(e)) page 950
Another name for etiologic fraction?
Attributable proportion/fraction
Population fractions?***
page 955-957
What is a null hypothesis?
there is no difference in pop. parameters among the groups being compared
P value?
indicates the probability that the findings observed could have occurred by chance alone
What is a confidence interval?
a CI is a statisitical measure. Computed interval of values that w/ a given probability, contains the true value of the population parameter/estimate
-Can be calculated for odds ration as well as other relative risks, etc.
What is a deterministic model?
it claims that a cause is invariably followed by an effect
- Ex: laws related to gravitation, motion, electrostatics
- from the philosophy of determinism
What is a necessary cause?
a factor whose presence is “required” for the occurrence of the effect
What is a sufficient cause?
a cause that is sufficient by itself to produce the effect
Deterministic causality?
- necessary and sufficient
- necessary but not sufficient
- sufficient but not necessary
- neither necessary nor sufficient
- pages 978-979
What is a stochastic process?
one that incorporates some element of randomness. A cause is associated with the increased probability that an effect will happen
-Ex: radiation exposure & carcinogenesis. Exposure to radiation from radioactive nuclear materials is related to the probability that the exposed person will develop radiation-induced cancer
What is multiple causation?
Also called multifactorial etiology. the requirement that more than one factor is present for a disease to develop.
What is the web of causation?
implicates broad classes of events and represents an incomplete portrayal of reality. a web like structure that intertwines different causes for a disease or something
-Figure 9-14 (page 982)
What is a wheel model?
explains the etiology of disease by calling into play host and environment interactions. similar to the epidemiologic triangle and web of causation w/ respect to multiple causality. another form
-Figure 9-15 (page 984)
What is the causal pie model?
indicates that a disease may be caused by more than one causal mechanism (a sufficient cause). another model of multiple causality
-Figure 9-16 (page 986)
What are significance tests?
a statistical procedure that when applied to a set of observations results in a p-value relative to some hypothesis
What is clinical significance?
describes the ability of a factor to impact health
- What is the benefit or harm yo people?
- Does the finding have practical application?
- Is there a clinically relevant benefit or harm?
- Are we sure the benefit
Large sample size produce?
Narrow CIs
Small sample size produce?
Wide CIs
Difference between absolute and relative effect?
Absolute effect looks at excess risk. Relative effect looks at the strength of association
If the exposure is positive?
It causes risk*
If the exposure is negative?
It is more protective*
What are the 3 measures of effect?
- Absolute effects
- Relative effects
- Attributable (etiologic) fractions
What is a risk factor?
an exposure that’s associated w/ a disease, morbidity, mortality, or adverse health outcome
Is a risk factor independent or dependent?
Independent; b/c it’s what causes the disease
Is a risk factor the same as risk? Why or why not?
No. A risk factor is not risk. Risk is the probability of developing the outcome (incidence)
Is outcome independent or dependent?
Dependent; b/c it’s the result of the exposure or risk factor
An absolute effect may be based on differences in what?
- Prevalence
- Cumulative incidence
- Incidence density
- Mortality
Relative risk?
RR; Ratio of risk for those exposed relative to not exposed
-(a/a+b) / (c/c+d)
Odds Ratio?
OR; Ratio of odds for those exposed relative to those not exposed
-ad/bc
Attributable risk?
Absolute excess risk among those exposed that is attributable to the exposure
-(a/a+b) - (c/c+d)
Attributable fraction?
Fraction of disease among those exposed that is attributed to the exposure
-(a/a+b) - (c/c+d) / (a/a+b)
What is association?
an identifiable relationship between exposure and disease
What is cause?
an agent or exposure that brings about an event or such as disease or other health outcome
