# Post Test Probability Calculator

```[text name="prevalence_percent" size=3] <-- Pretest Prevalence (%)
[text name="total" default=1000 size=6] <-- Population
[text name="sensitivity_percent" size=3] <-- Sensitivity (%)
[text name="specificity_percent" size=3] <-- Specificity (%)
True positive: [calc value="A=((((prevalence_percent)/(100))*(total)*((sensitivity_percent)/(100)))/((1)-((sensitivity_percent)/(100)))/((1) + ((sensitivity_percent)/(100))/((1)-((sensitivity_percent)/(100))))).toFixed(0)" memo="true +"] --- False positive: [calc value="B=(((1-((prevalence_percent)/(100)))*(total)) - (((total) - ((total)*((prevalence_percent)/(100))))/(((1-((specificity_percent)/(100)))/((specificity_percent)/(100)))+1))).toFixed(0)" memo="false +"]

False negative: [calc value="C=((((prevalence_percent)/(100))*(total))/((1+((((sensitivity_percent)/(100)))/(1-((sensitivity_percent)/(100))))))).toFixed(0)" memo="false -"] --- True negative: [calc value="D=(((total) - ((total)*((prevalence_percent)/(100))))/(((1-((specificity_percent)/(100)))/((specificity_percent)/(100)))+1)).toFixed(0)" memo="true -"]

Likelihood Ratio (+):  [calc value="LRplus=((A)/(B)).toFixed(3)" memo="+ LR"]

Likelihood Ratio (-) = [calc value="LRneg=((D)/(C)).toFixed(3)" memo="- LR"]

Positive Predictive Value: [calc value="PPV=(((A)*(1))/(((A)*(1))+((B)*(1)))).toFixed(3)" memo="+ PPV"]

Negative Predictive Value: [calc value="PPV=(((D)*(1))/(((D)*(1))+((C)*(1)))).toFixed(3)" memo="- PPV"]```
<-- Pretest Prevalence (%)
<-- Population
<-- Sensitivity (%)
<-- Specificity (%)
True positive: true +A=((((prevalence_percent)/(100))*(total)*((sensitivity_percent)/(100)))/((1)-((sensitivity_percent)/(100)))/((1) + ((sensitivity_percent)/(100))/((1)-((sensitivity_percent)/(100))))).toFixed(0) --- False positive: false +B=(((1-((prevalence_percent)/(100)))*(total)) - (((total) - ((total)*((prevalence_percent)/(100))))/(((1-((specificity_percent)/(100)))/((specificity_percent)/(100)))+1))).toFixed(0)

False negative: false -C=((((prevalence_percent)/(100))*(total))/((1+((((sensitivity_percent)/(100)))/(1-((sensitivity_percent)/(100))))))).toFixed(0) --- True negative: true -D=(((total) - ((total)*((prevalence_percent)/(100))))/(((1-((specificity_percent)/(100)))/((specificity_percent)/(100)))+1)).toFixed(0)

Likelihood Ratio (+): + LRLRplus=((A)/(B)).toFixed(3)

Likelihood Ratio (-) = - LRLRneg=((D)/(C)).toFixed(3)

Positive Predictive Value: + PPVPPV=(((A)*(1))/(((A)*(1))+((B)*(1)))).toFixed(3)

Negative Predictive Value: - PPVPPV=(((D)*(1))/(((D)*(1))+((C)*(1)))).toFixed(3)

Sandbox Metrics: Structured Data Index 0, 12 form elements, 34 boilerplate words, 4 text boxes, 8 calculations, 4 total clicks
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