measures of association

Question 1

measures of association

Answer 1

quantify the relationship between exposure and disease/outcome among the two groups

Question 2

three measures of association

Answer 2

1. relative risk = incidence in exposed/ incidence in unexposed
2. risk difference = incidence in exposed - incidence in unexposed
3. odds ratio= odds of exposure in cases/ odds of exposure in controls

Question 3

relative risk equation

Answer 3

= incidence in exposed/ incidence in unexposed

Question 4

what does RR tell us

Answer 4

tells us the strength of the association, how closely linked the exposure is to the outcome

Question 5

three outcomes of RR

Answer 5

1) RR> 1 meaning there is a greater likelihood of the outcome in the exposed group risk factor if the outcome is bad
2) RR=1, the RR null value, no association between exposure and outcome
3) RR<1, meaning there is a greater likelihood of the outcome in the unexposed group, protective factor if the outcome is bad

Question 6

risk difference

Answer 6

= incidence in exposed- incidence in unexposed

• RD tells us the impact of the exposure, how much of the outcome is due to the exposure, and how much disease we would prevent by removing the exposure

Question 7

outcomes of calculating RD

Answer 7

1) RD> 0 meaning there is a greater likelihood of the outcome in the exposed group, risk factor if the outcome is bad
2) RD=0, the RD null value, no association between exposure and outcome
3) RD<0 meaning there is a greater likelihood of the outcome in the unexposed group, protective factor if the outcome is bad

Question 8

odds ratio

Answer 8

• measure of association for case control studies (only)
• an approximation for relative risk

Question 9

odds ratio equation

Answer 9

odds ratio= odds of exposure in cases/ odds of exposure in controls

= (exposed cases/unexposed cases)/(exposed control/unexposed controls)

Question 10

odds ratio outcome

Answer 10

1) odds ratio> 1 means that exposure may be a risk factor for the disease
2) odds ratio= 1, null value, no association between exposure and outcome
3) odds ratio < 1 means that the exposure may be a protective factor for the disease