Attributable risk percent
Talk0
34,135pages on
this wiki
this wiki
Redirected from Percent attributable risk
Assessment 
Biopsychology 
Comparative 
Cognitive 
Developmental 
Language 
Individual differences 
Personality 
Philosophy 
Social 
Methods 
Statistics 
Clinical 
Educational 
Industrial 
Professional items 
World psychology 
Statistics: Scientific method · Research methods · Experimental design · Undergraduate statistics courses · Statistical tests · Game theory · Decision theory
Epidemiology

Measures of occurrence 
Measures of association 

Other measures 
By mental health disorder 

Attributable risk percent (ARP) is a calculation that can be derived from attributable risk.^{[1]}
It gives the portion of cases attributable (and avoidable) to this exposure in relation to all cases.
It can be calculated as (relative risk  1) / relative risk.^{[1]}
Worked exampleEdit
Example 1: risk reduction  Example 2: risk increase  

Experimental group (E)  Control group (C)  Total  (E)  (C)  Total  
Events (E)  EE = 15  CE = 100  115  EE = 75  CE = 100  175 
Nonevents (N)  EN = 135  CN = 150  285  EN = 75  CN = 150  225 
Total subjects (S)  ES = EE + EN = 150  CS = CE + CN = 250  400  ES = 150  CS = 250  400 
Event rate (ER)  EER = EE / ES = 0.1, or 10%  CER = CE / CS = 0.4, or 40%  EER = 0.5 (50%)  CER = 0.4 (40%) 
Equation  Variable  Abbr.  Example 1  Example 2 

CER − EER  < 0: absolute risk reduction  ARR  (−)0.3, or (−)30%  N/A 
> 0: absolute risk increase  ARI  N/A  0.1, or 10%  
(CER − EER) / CER  < 0: relative risk reduction  RRR  (−)0.75, or (−)75%  N/A 
> 0: relative risk increase  RRI  N/A  0.25, or 25%  
1 / (CER − EER)  < 0: number needed to treat  NNT  (−)3.33  N/A 
> 0: number needed to harm  NNH  N/A  10  
EER / CER  relative risk  RR  0.25  1.25 
(EE / EN) / (CE / CN)  odds ratio  OR  0.167  1.5 
EER − CER  attributable risk  AR  (−)0.30, or (−)30%  0.1, or 10% 
(RR − 1) / RR  attributable risk percent  ARP  N/A  20% 
1 − RR (or 1 − OR)  preventive fraction  PF  0.75, or 75%  N/A 
ReferencesEdit
 ↑ ^{1.0} ^{1.1} Cole P, MacMahon B (November 1971). Attributable risk percent in casecontrol studies. Br J Prev Soc Med 25 (4): 242–4.
Biomedical research: Clinical study design / Design of experiments  

Overview  
Controlled study (EBM I to II1; A to B)  
Observational study (EBM II2 to II3; B to C)  
Epidemiology/ methods 

Trial/test types  
Analysis of clinical trials  
Interpretation of results  
* Category 
This page uses Creative Commons Licensed content from Wikipedia (view authors). 