Disease/Test Relation Calculators

File Name
(Click the ".xls" file, hold mouse button, select "save as" to download)

Calculator Name

Function of Calculator

2x2count.xls

 

Tutorial

 

Web Calculator (Vassar)

Contingency table (test by disease): counts from probabilities

You specify base rate, sensitivity, specificity, it produces counts in 2 by 2 table plus other statistics.

2x2probs.xls

Tutorial

 

Web Calculator (CEBM)

Contingency table (test by disease): probs. from counts

You put counts in cells of 2 by 2 table, it produces sensitivity, specificity, etc.

2x2p&ci.xls

Tutorial

Contingency table (test by disease) with confidence intervals on each probability

As with 2x2probs, you put counts in cells of 2 by 2 table; it produces the list of probabilities, and gives the confidence interval for each.

baystree.xls

Decision Tree: Bayes' Theorem

You specify base rate, specificity, and sensitivity. It demonstrates "inversion" of a tree.

lhoodrat.xls

 

Web Nomogram

Bayes' Theorem in the Odds/Likelihood ratio form

You specify Prior Odds the patient has disease, and likelihood ratio of seeing test results, given patient has the disease or does not have the disease; it calculates posterior odds.

LogBayes.xls

Log Odds Version of Bayes’ Theorem

You specify prior probability, sensitivity, specificity, and test result for a series of tests. It graphs Bayes' Theorem calculations in Log(odds) scale.

baysgrph.xls

Bayesian graph

You specify sensitivity and specificity of a test, it prints posterior probability as a function of any prior probability.

baysgrmg.xls

Bayesian graph for diseases with low prior probability

You specify sensitivity and specificity of a test, for a disease with a low prior probability (less than 10%). It prints posterior probability as a function of prior probability in the 0 to 0.1 range.

baygphth.xls

Bayesian graph with thresholds

As with Bayesian graph; plus you specify a treatment threshold and it specifies and graphs a No-test/Test Threshold and a Test/Treat Threshold.

bgphthut.xls

Bayesian graph with thresholds based on utilities

As with Bayesian graph with thresholds; plus you specify the utilities upon which a threshold would be based.

ScrnPers.xls

Screening perspective calculator

You specify the base rate for a condition, the number of people screened, and the sensitivity and specificity of a screening test, and it displays a tree showing the numbers with/without the disease and with true and false screen results.

Entropy-Uncertainty.xlsx

Explore the use of “negative entropy” to measure uncertainty

You specify prior probability of a disease, and the sensitivity and specificity of a test. It shows probability of a positive or negative test, post test result probabilities, the pretest uncertainty, and the expected posttest uncertainty.

2tstindp.xls

 

Tutorial

 

Presentation European Society MDM 1999

Explore implications of 2 diagnostic tests - are they independent or correlated?

You specify the characteristics of a disease (prior probability) and of 2 diagnostic tests for it (sensitivities and specificities, and correlation between them when disease is present and when absent). It constructs the corresponding data set, and gives post test probabilities for all combinations of test results.

3tstindp.xls

Explore implications of 3 diagnostic tests - are they independent or correlated?

You specify the characteristics of a disease (prior probability) and of 3 diagnostic tests for it (sensitivities and specificities, and correlation between them when disease is present and when absent). It constructs the corresponding data set, gives post test probabilities for all combinations of test results.