Preventive fraction
this wiki
Ad blocker interference detected!
Wikia is a freetouse site that makes money from advertising. We have a modified experience for viewers using ad blockers
Wikia is not accessible if you’ve made further modifications. Remove the custom ad blocker rule(s) and the page will load as expected.
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 

Preventive fraction (PF), also called preventable fraction, is a calculation that can be derived from relative risk or odds ratio.
It may be used when an exposure seems to reduce the risk (in opposition to attributable risk percent), and gives the percentage of cases that can be prevented if a population is exposed to an intervention, compared to an unexposed population.
It can be calculated as ( 1 − relative risk ) or as ( 1 − odds ratio ).^{[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
 ↑ Aschengrau, Ann (2003). Essentials of epidemiology in public health, 65–66, Jones & Bartlett Publishers.
This page uses Creative Commons Licensed content from Wikipedia (view authors). 