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#1




25 biostats equations
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 don't try to memorize these equations... the list is here to help illustrate the pattern. i tried to organize these equations in a way that's easy to follow, but if you would like a better visual presentation, check out my youtube video... List of Equations Last edited by Kruno; 04072016 at 12:22 AM. 
#2




How To Calculate Sensitivity ...if you know the number of true positives and the total number of people with the disease ...if you know the prevalence of the disease, the number of positive tests, and the positive predictive value Specificity ...if you know the number of true negatives and the total number of people without the disease ...if you know the prevalence of the disease, the number of negative tests, and the negative predictive value False negative rate ...if you know the number of false negatives and the total number of people with the disease False positive rate ...if you know the number of false positives and the total number of people without the disease
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#3




Definitions and Equations
Definitions and Equations
Here is the same list, but with a youtube link for each equation. These short videos show the definition and briefly explain how to make the calculation. 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
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#4




stepbystep
here is new playlist of quick calculations for the 25 biostats equations in my EpiStats channel. the videos use a biostats calculator (which has a sample table) to show each step that is required to make the calculation.
Absolute Risk Reduction Accuracy Attributable Risk False Discovery Rate False Negative Rate False Omission Rate False Positive Rate Informedness Incidence Markedness Negative Likelihood Ratio Number Needed To Harm Number Needed To Treat Negative Predictive Value Odds of Exposure (Cases) Odds of Exposure (Controls) Odds Ratio Positive Likelihood Ratio Positive Predictive Value Precision Prevalence Relative Risk Relative Risk Reduction Sensitivity Specificity
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#5




equations
i have almost completed a playlist of animated lectures which demonstrate how to make each calculation, but in the meantime.... here is the equations table from the quick info section of the EpiStats app
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