Lecture 17 9/24/24

Question 1

What is risk?

Answer 1

a proportion of an entire population developing a given outcome

Question 2

What is odds?

Answer 2

ratio of those with and without the outcome within the population

Question 3

What is the relationship between odds and risk?

Answer 3

-as risk decreases, odds and risk become closer and closer
-virtually identical when risk is < 10%

Question 4

What is risk ratio?

Answer 4

how many times more likely exposed individuals are to become diseased relative to non-exposed individuals

Question 5

How is risk ratio calculated?

Answer 5

RR = incidence in exposed/incidence in non-exposed

Question 6

What provides information regarding the magnitude of effect/strength of association when interpreting relative risk?

Answer 6

obtained point estimate

Question 7

What provides information regarding the significance of relative risk?

Answer 7

95% confidence interval

Question 8

How is the risk ratio/relative risk point estimate interpreted?

Answer 8

-if =1, risk in exposed is equal to risk in unexposed
-if >1, risk in exposed is greater than risk in unexposed
-if <1, risk in exposed is less than risk in unexposed

Question 9

How is the risk ratio/relative risk conf. interval interpreted?

Answer 9

-if 1 is included, the ratio is not statistically significant and there is no association
-if lower limit of CI is >1, risk in exposed is significantly greater than risk in unexposed
-if upper limit of CI is <1, risk in exposed is significantly lower than risk in unexposed

Question 10

What provides information regarding the magnitude of effect/strength of association when interpreting odds ratio?

Answer 10

obtained point estimate

Question 11

What provides information regarding the significance of odds ratio?

Answer 11

confidence interval

Question 12

How is the odds ratio point estimate interpreted?

Answer 12

-if =1, odds of exposure in diseased equals odds of exposure in non-diseased
-if >1, odds of exposure in diseased greater than odds of exposure in non-diseased
-if <1, odds of exposure in diseased less than odds of exposure in non-diseased
*all of these work when evaluating odds of disease in exposed vs un-exposed as well

Question 13

How is the odds ratio conf. interval interpreted?

Answer 13

-if 1 is included, ratio is not statistically significant and there is no association
-if lower limit of CI is >1, odds in exposed is significantly greater than odds in unexposed
-if upper limit of CI is <1, odds in exposed is significantly less than odds in unexposed

Question 14

What is risk difference?

Answer 14

-the risk of disease in the exposed group minus the risk of disease in the non-exposed group
-RD = incidence in exposed - incidence in non-exposed

Question 15

How is a risk difference interpreted?

Answer 15

positive difference:
-for every XX cats on Z treatment, ## developed outcome due to taking Z treatment
negative difference:
-for every XX cats on Z treatment, ## did not develop outcome due to taking Z treatment

Question 16

How is the point estimate of RD interpreted?

Answer 16

-if RD = 0, exposure has no effect
-if RD > 0, exposure is positively associated with disease
-if RD < 0, exposure is protective

Question 17

What is attributable fraction?

Answer 17

-expresses proportion of disease in exposed individuals that is due to exposure (assuming causal relationship)
-proportion of disease in exposed group that would have been avoided if the exposure were removed

Question 18

How is the point estimate for attributable fraction interpreted?

Answer 18

-if AF = 0, risk is equal regardless of exposure
-if AF is > 0 up to 1, no disease in the non-exposed group and disease is due to exposure
-if AF < 0, exposure is protective

Question 19

What is population attributable risk?

Answer 19

indicates the increase in risk of disease in the population that is attributable to the exposure

Question 20

What factors into population attributable risk?

Answer 20

-strength of association
-frequency of exposure to risk factor

Question 21

How is population attributable risk interpreted?

Answer 21

for every XX animals in pop., ## developed disease X due to risk factor

Question 22

What is population attributable fraction?

Answer 22

-expresses proportion of disease in the population that is due to the exposure
-proportion of disease in pop. that would have been avoided if exposure were removed