



Clinical
Decision Making Calculators
The CDM calculators are of the
following types:
Judgment Research
Calculators
Decision Analysis
Calculators
Disease/Test Relation
Calculators
Exposure/Disease Relation Calculators
Treatment/Outcome Relation
Calculators
Calculators Useful
in the Clinic
Statistics Calculators
Tutorials for some of
the calculators
Comparison
of Webbased versus spreadsheet calculators. (Presented at Aerospace Human
Factors Society meetings, Detroit, May 20, 1999.)
Each
spreadsheet performs a common calculation useful for clinical decisions or
for analyzing data pertinent to clinical decisions.
You
must download the files, then run them using your
own spreadsheet program. Hold down the mouse button (PC  right button) and select
"Save link as..." to download the file. These are Excel files, and
their extension is .XLS or .XLSX.
They run on Macintosh or DOS/Windows computers.
After
you have downloaded the files, you might find it necessary to open your
spreadsheet, then load the file using the
spreadsheet's "open" command, rather than clicking on the name of
the file, because your operating system may not recognize that an ".XLS" file is a spreadsheet file.
(If
your browser does not download these correctly when you click on them.)
These
calculator spreadsheets are made available by Rob Hamm,
PhD, in the Clinical Decision Making Program, Department of Family
and Preventive Medicine, University
of Oklahoma Health Sciences Center
Judgment
Research Calculators
File
Name
(Click,
hold mouse button, select "save as" to download)

Calculator
Name

Function
of Calculator

CueCorrels.xlsx

Correlated Cues for
Judgment Study Stimuli

To generate a set
of stimulus objects for study participants to make judgments about, with
desired correlations between criterion and cues, and among (some of) the
cues.

Decision Analysis Calculators
File
Name
(Click,
hold mouse button, select "save as" to download)

Calculator
Name

Function
of Calculator

eutree.xls

Decision Tree:
Expected Utility

You
specify probabilities of branches and utilities of outcomes, it calculates expected utility.

discount.xls
discountmonths.xls

Utility Discount
Rate

Calculates a
person's temporal discount rate. Assumes person has already made a judgment
setting equivalent two life streams  one with a time of sickness at the
beginning, the other with a period of sickness at the end.
If either time period is measured in months, use "discountmonths.xls"
which is very large.

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 Notest/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.

EntropyUncertainty.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 for Medical Decision Making, 1999)

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

You specify the
characteristics of 2 diagnostic tests for a disease (prior probability,
sensitivities and specificities, and correlation 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 3 diagnostic tests for a disease (prior probability,
sensitivities and specificities, and correlations when disease is present
and when absent. It constructs the corresponding data set, gives post test probabilities for
all combinations of test results.

File
Name
(Click
hold mouse button, select "save as" to Download)

Calculator
Name

Function
of Calculator

exposdis.xls
Web Calculator (CEBM)

Contingency table
showing outcomes (disease) as an effect of exposure

You specify data
about the relation between exposure and disease,
it produces statistics (relative risk, etc.)

NNP.xls

Number Needed to
Protect

You specify the effect
of an exposure (probability of bad outcome without the exposure and with
the exposure), it produces the number of people
you would need to protect to prevent one bad outcome.

NNPcost.xls

Number Needed to
Protect and Cost

You specify the
effect of an exposure (probability of bad outcome without the exposure and
with the exposure), it produces the number of
people you would need to protect to prevent one bad outcome. You specify the
cost of protecting one person from exposure. It says whether it is worth
protecting a person from exposure, and gives thresholds on NNP and Cost of Protecting.

oddsrat.xls

Odds ratio:
contingency between treatment or exposure and outcome

You specify the
contingency table, it calculates odds ratio. Allows this to be done from various starting points.

2trtindp.xls

2 Treatment
Independence

To explore
dependencies between exposure to two risk factors
or treatments. One dependency is correlation between the factors. The other
dependency is the effects of one factor being different for different levels
of the other factor.

2trtindpkram.xls
Tutorial

2 Treatment
Independence, diagnosis framework

To explore
dependencies between exposure to two risk factors
or treatments. This follows Kraemer et al (1999 Psychological Methods) in
speaking of the "sensitivity" and "specificity" of the
risk factor for the outcome. In calculation, it is identical to the 2 Test Independence
calculator (see above) and so you can use that one's tutorial. The
dependencies are the correlations between the two risk factors' false
negatives, and between their false positives.

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

Calculator Name

Function of Calculator

treatout.xls
Treatout tutorial
Web
Calculator (CEBM)

Contingency table:
outcome as an effect of treatment

You specify the
data relating treatment to outcome, it calculates odds ratio, etc.

casecont.xls

Contingency table
statistics appropriate for case/control designs.

You enter data from
a case control study, it produces valid statistics
for generalization.

besd.xls

Binary Effect Size
Display (BESD)

You specify a
contingency table showing an effect (treatment/outcome), it expresses the
relation as correlation, etc.

NNT.xls

Number needed to
treat

You specify the
effect of a treatment (probability of bad outcome without the treatment and
with the treatment), it produces the number of
patients you would need to treat to prevent one bad outcome.

NNTcost.xls

Number Needed to
Treat and Cost

You specify the
effect of a treatment (relating the probability of bad outcome without the
treatment and with the treatment), it produces the
number of people you would need to treat to prevent one bad outcome. You
specify the cost of treating one person. It says whether it is worth
treating one person, and gives thresholds on NNT
and Cost of Treating.

oddsrat.xls

Odds ratio:
contingency between treatment or exposure and outcome

You specify the
contingency table, it calculates odds ratio. Allows this to be done from various starting points.

ORexplor.xls

Odds Ratio explorer
 from retrospective to prospective context

Demonstrates why it
is appropriate to use the Odds Ratio derived from a case control study, in
a prospective context, and why OR is a good "control variable"
for a sensitivity analysis.

Yearates.xls

Yearly Rates.

Translates outcome
rates for treated and nontreated conditions (or
Odds Ratio) in a multiyear study into annual rates.

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

Calculator
Name

Function
of Calculator

BMI.xls
Web
calculator (by Jim Cacy, in JavaScript)

Body Mass Index

You
specify height, weight (in metric or English units), it calculates Body Mass Index.

FPIR.xls

Family Practice
Incidence Rate

You specify the
size of a doctor's practice, and the rate a disease occurs. It specifies
the number the doctor could expect to see in a year.

NmNeedTr.xls

Number needed to
treat

You specify the
effect of a treatment (probability of bad outcome without the treatment and
with the treatment), it produces the number of
patients you would need to treat to prevent one bad outcome.

File
Name
(Click
hold mouse button, select "save as" to Download)

Calculator
Name

Function
of Calculator

Confin95.xls

95% confidence
intervals

You specify the
confidence interval you are interested in, it calculates the interval
around an effect size estimate for: differences,
relative risk, relative risk reduction, and odds ratio.

ProbCI.xls

Confidence interval
for probabilities, proportions

You specify the
number of events and the total number of observations,
it calculates the confidence interval for that probability.

fishersz.xls

Fisher
ztransformation for doing statistical tests on correlations

You specify correlation, it produces Fisher's Z transformation. And the reverse.

logit.xls

Logit and logistic
functions demonstrated

You state a number,
it produces the logit; likewise for the logistic function (inverse of the
logit). Demonstrates the basis of logistic regression for predicting the
probability of a category.

oddprob.xls

Odds and
probabilities

Translates between
odds and probabilities. Graphs the relations.

Chisq2x2.xls

Chisquared
test

Calculates
Chisquared statistic and probability for 2 by n tables, for n = 2 through
7.

RatePower.xls

Rate or Proportion
Confidence Interval & Power Estimation Calculator

Calculate the power
that a rate will exceed a target rate given N.

TripTria.xls

Triplet
Triangulator

Places
a triplet of numbers in trilinear coordinates within a triangle.

Questions? Contact:
Robert
M. Hamm, PhD, Professor
Director,
Clinical Decision Making Program
Department
of Family and Preventive Medicine
University
of Oklahoma Health Sciences Center
900
NE 10th Street
Oklahoma
City, OK 73104
Phone
(405) 2715362 x 32306 Fax (405) 2712784
roberthamm@ouhsc.edu
http://www.fammed.ouhsc.edu/robhamm/index2.htm
