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lets make a marker board formula list for step - shigatox22 - Printable Version +- USMLE Forum - Largest USMLE Community (https://www.usmleforum.com) +-- Forum: USMLE Forum (https://www.usmleforum.com/forumdisplay.php?fid=1) +--- Forum: Step 1 (https://www.usmleforum.com/forumdisplay.php?fid=2) +--- Thread: lets make a marker board formula list for step - shigatox22 (/showthread.php?tid=629048) Pages:
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lets make a marker board formula list for step - shigatox22 - ArchivalUser - 11-07-2011 c'mon guys i think this is really useful n will help our brains have memory for the more impt things ... lets make a list of impt formulas if u guys respond but the subject name like bistat forumla or pharm forumula n we will come up with a high yeild formula list!! thanks 0 - ArchivalUser - 11-07-2011 BIOSTATS: PREVALANCE estimates----- INCIDENCE X (DISEASE DURATION) PPV=TP/TP+FP NPV=TN/TN+FN SPECIFICITY=TN/TN+FP SENSITIVITY=TP/TP+FN ODDS ratio=AD/BC RR=A/(A+B) divided C/(C+D) ATTRIBUTABLE RISK= A/A+B (-) C/C+D ..INVERSE OF FRACTION IS NNT OR numbr needed to harm 0 - ArchivalUser - 11-07-2011 hi shigatox22 ..nice effort correction : NNT and NNH are diff NNH= 1/ AR ( attributable risk ) ie. {a/a+b}- {c/c+d} NNT = 1/ARR (Absolute risk reduction ) ie (rate in control) - (rate in treatment /exposed) how i remember to avoid confusion is tht No. Needed to HARM has 'AR' in it so it is associated with AR attributable risk ( not abs risk reduction which is ARR) 0 - ArchivalUser - 11-07-2011 hmm kaplan guy says AR and ARR is the same thing.....AR asses actual RISK of disease.....and ARR asses actual RISK REDUCTION of disease as NNT asses how many ppl to affect to 1 life n as NNH asses how many ppl to harm to affect 1 life basically the equations are identical for AR n ARR but....... AR=Incidence in exposed group (-) incidence in unexposed group thus ARR= Incidence in tx group (-) Incidence in placebo(control) group 0 - ArchivalUser - 11-07-2011 RELATIVE RISK REDUCTION= INCIDENCE in tx group (-) INCIDENCE in control(placebo) group DIVIDED by INCIDENCE IN control(placebo) group 0 - ArchivalUser - 11-07-2011 i know the actual definition is diff but were just worried at this point of memorizing the forumulas cuz it should be expected that everyone knows how to apply it to a question CORRECT ME IF UM WRONG PPL 0 - ArchivalUser - 11-08-2011 bump 0 - ArchivalUser - 11-08-2011 You are right. Relative Risk Reduction (RRR) = Absolute Risk Reduction (ARR)/Control Event Rate (CER) 0 - ArchivalUser - 11-08-2011 ARI= absolute risk increase, AR= Absolute risk, RR= relative risk, ARR=absolute risk reduction, RRR= relative risk reduction, ARP = Attributable risk percent, (AR) control = AR of control NNH = 1/ ARI NNT = 1/ ARR ARI = Event rate of treatment - event rate of control ARR = Event rate of control - event rate of treatment Event rate of treatment = Events/ total treatment arm subjects RRR = ((AR)control - (AR)treatment ) / (AR) control ARP = (Risk in exposed - Risk in unexposed)/ Risk in exposed ARP = (RR-1)/RR ARP is the attributable risk percent that represents the excess risk in the exposed population that can be attribute to the risk factor. 0 - ArchivalUser - 11-08-2011 thanks lets keep it goin guys |