Chapter 9: Measures of Effect

Question 1

What is an effect measure?

Answer 1

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

Question 2

What is the difference measure of association?

Answer 2

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

Question 3

What is another name for difference measure of association?

Answer 3

Attributable risk

Question 4

Risk difference?

Answer 4

the difference between the incidence rate of disease in an exposed group and a non exposed group
-RD= I(e)-I(ne)

Question 5

Population risk difference?

Answer 5

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)*

Question 6

What is an etiologic fraction? Equation?*

Answer 6

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

Question 7

Another name for etiologic fraction?

Answer 7

Attributable proportion/fraction

Question 8

Population fractions?***

Answer 8

page 955-957

Question 9

What is a null hypothesis?

Answer 9

there is no difference in pop. parameters among the groups being compared

Question 10

P value?

Answer 10

indicates the probability that the findings observed could have occurred by chance alone

Question 11

What is a confidence interval?

Answer 11

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.

Question 12

What is a deterministic model?

Answer 12

it claims that a cause is invariably followed by an effect

• Ex: laws related to gravitation, motion, electrostatics
• from the philosophy of determinism

Question 13

What is a necessary cause?

Answer 13

a factor whose presence is “required” for the occurrence of the effect

Question 14

What is a sufficient cause?

Answer 14

a cause that is sufficient by itself to produce the effect

Question 15

Deterministic causality?

Answer 15

• necessary and sufficient
• necessary but not sufficient
• sufficient but not necessary
• neither necessary nor sufficient
• pages 978-979

Question 16

What is a stochastic process?

Answer 16

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

Question 17

What is multiple causation?

Answer 17

Also called multifactorial etiology. the requirement that more than one factor is present for a disease to develop.

Question 18

What is the web of causation?

Answer 18

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)

Question 19

What is a wheel model?

Answer 19

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)

Question 20

What is the causal pie model?

Answer 20

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)

Question 21

What are significance tests?

Answer 21

a statistical procedure that when applied to a set of observations results in a p-value relative to some hypothesis

Question 22

What is clinical significance?

Answer 22

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

Question 23

Large sample size produce?

Answer 23

Narrow CIs

Question 24

Small sample size produce?

Answer 24

Wide CIs

Question 25

Difference between absolute and relative effect?

Answer 25

Absolute effect looks at excess risk. Relative effect looks at the strength of association

Question 26

If the exposure is positive?

Answer 26

It causes risk*

Question 27

If the exposure is negative?

Answer 27

It is more protective*

Question 28

What are the 3 measures of effect?

Answer 28

• Absolute effects
• Relative effects
• Attributable (etiologic) fractions

Question 29

What is a risk factor?

Answer 29

an exposure that’s associated w/ a disease, morbidity, mortality, or adverse health outcome

Question 30

Is a risk factor independent or dependent?

Answer 30

Independent; b/c it’s what causes the disease

Question 31

Is a risk factor the same as risk? Why or why not?

Answer 31

No. A risk factor is not risk. Risk is the probability of developing the outcome (incidence)

Question 32

Is outcome independent or dependent?

Answer 32

Dependent; b/c it’s the result of the exposure or risk factor

Question 33

An absolute effect may be based on differences in what?

Answer 33

• Prevalence
• Cumulative incidence
• Incidence density
• Mortality

Question 34

Relative risk?

Answer 34

RR; Ratio of risk for those exposed relative to not exposed

-(a/a+b) / (c/c+d)

Question 35

Odds Ratio?

Answer 35

OR; Ratio of odds for those exposed relative to those not exposed
-ad/bc

Question 36

Attributable risk?

Answer 36

Absolute excess risk among those exposed that is attributable to the exposure
-(a/a+b) - (c/c+d)

Question 37

Attributable fraction?

Answer 37

Fraction of disease among those exposed that is attributed to the exposure
-(a/a+b) - (c/c+d) / (a/a+b)

Question 38

What is association?

Answer 38

an identifiable relationship between exposure and disease

Question 39

What is cause?

Answer 39

an agent or exposure that brings about an event or such as disease or other health outcome