Risk and Probability PDF

2/12/25, 11:54 AM OneNote Risk and Probability Tuesday, January 21, 2025 9:29 AM What is risk? Absolute risk= the risk of something happening over a specific period of time...

2/12/25, 11:54 AM OneNote Risk and Probability Tuesday, January 21, 2025 9:29 AM What is risk? Absolute risk= the risk of something happening over a specific period of time ○ Ex: risk of developing a disease over a 10 year perios, over your lifetime etic. Reletive risk= risk compared between 2 groups ○ Ex: risk for those who smoke relitive to those who don’t ○ Can tell us how much we can chanfe our risj through a behavoural change Hypothetical example: CVD and smoking: Follow 50 people for 10 years ○ 25 are smkers (triagnles) ○ 25 are non-smokers (circles) How many developed disease (CVD)? Hypothetical example: CVD and Cmoking Follow 50 people for 10 years 25 are smokers (tringles) 25 are non-smokers (circles) How many devloped disease (CVD)? 19 develpped CVD- orage shapes 31 did not – purple Calcultaing absolute risk in each group: https://uvic-my.sharepoint.com/personal/lucybryden_uvic_ca/_layouts/15/Doc.aspx?sourcedoc={9faa0b91-e898-498c-a6e1-c5e15b84c2ef}&action=edit&wd=target… 1/4 2/12/25, 11:54 AM OneNote Calculating Relative Risk (Risk Ratio): Relative Risk Interpretation If the relative risk is ~1 it suggests no difference or little difference in risk between the groups A relative risk > 1 suggests an increased risk in the exposed group. ○ E.g., relative risk = 1.5 means 1.5X the risk as in exposed group A relative risk < 1 suggests a reduced risk in the exposed group ○ E.g., relative risk = 0.5 means 0.5X (or half) the risk in exposed group ○ What is % change in reltive risk: An examoke: brest cancer risk: Risk and Breast Cancer Absolute risk of developing breast cancer at some point during life in the general population (U.S. women) is 12.9% Women who started smoking