Prep for USMLE 
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Kruno
Forum Newbie Topics: 0 Posts: 11 
not all of these equations are important for the usmle, but its helpful to learn a few. and if you know a little biostats and can visualize a two by two sample table, then you can probably figure out most of them. Sensitivity = A / (A+C) False Negative Rate = C / (A+C) Specificity = D / (B+D) False Positive Rate = B / (B+D) Positive Predictive Value = A / (A+B) False Discovery Rate = B / (B+D) Negative Predictive Value = D / (C+D) False Omission Rate = C / (C+D) Positive Likelihood Ratio = [A / (A+C)] / [B / (B+D)] Negative Likelihood Ratio = [C / (A+C)] / [D / (B+D)] Informedness = [A / (A+C)] + [D / (B+D)]  1 Markedness = [A / (A+B)] + [D / (C+D)]  1 Accuracy = (A+D) / (A+B+C+D) Precision = A / (A+B) Relative Risk = [A / (A+B)] / [C / (C+D)] Relative Risk Reduction = 1  [A / (A+B)] / [C / (C+D)] Absolute Risk Reduction = [C / (C+D)]  [A / (A+B)] Number Needed To Treat = 1 / [C / (C+D)]  [A / (A+B)] Attributable Risk = [A / (A+B)]  [C / (C+D)] Number Needed To Harm = 1 / [A / (A+B)]  [C / (C+D)] Odds of Exposure (Cases) = A / C Odds of Exposure (Controls) = B / D Odds Ratio = (A / C) / (B / D) Prevalence = [(A+C) / (A+B+C+D)] Incidence = [(A+C) / (A+B+C+D)] / Time Period i tried to organize these equations in a way thats easy to follow. but if you would like a better visual presentation, check out my youtube video... https://www.youtube.com/watch?v=r8DU......drh&index=2 __________________ EpiStats Lectures on common equations in epidemiological biostatistics... from absolute risk reduction to specificity. https://www.youtube.com/channel/UCQ3...b0Jy0MlX12f4cg  
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