Web Pages that Perform Statistical
Calculations
Calculating Pages...
Selecting the right kind of analysis
Calculators, plotters, function integrators, and
interactive programming environments
Probability distribution functions: tables, graphs,
random number generators
Descriptive statistics, histograms, charts
Confidence intervals, single-population tests
Sample comparisons: t-tests, ANOVAs,
non-parametric comparisons
Contingency tables, cross-tabs, Chi-Square tests
Regression, correlation, least squares
curve-fitting, non-parametric correlation
Analysis of survival data
Bayesian Methods
Other statistical tests and analyses
Specialized and discipline-specific tests and
analyses
Power, sample size and experimental design
Other Statistical Resources...
There are a bewildering number of statistical analyses out there, and choosing the
right one for a particular set of data can be a daunting task. Here are some web pages
that can help:
- "Selecting
Statistics", by Bill Trochim (Cornell). This is an interactive set of web pages
to help you select the right kind of analysis to perform on your data. It asks you a
simple series of questions about your data (how many variables, etc.), then makes
recommendations about the best test to perform.
- Choosing a Statistical Test,
Chapter 37 of Dr. Harvey Motulsky's book Intuitive Biotatistics.
- The very extensive
test-selection routine used in Dr. Robert Knodt's MODSTAT statistical package.
- The WebMath page performs a large number of
numeric calculations and symbolic algebraic manipulations of the type that might arise in
high school / college algebra and calculus, including some elementary statistical
calculations. In doing so, it provides a detailed step-by-step explanation of how it
arrived at the answer.
- Expression Evaluators -- type in any numeric expression; the
computer will evaluate it and display the results...
- Scientific Calculator (numeric
expression evaluator) (JavaScript)
- Expression
Evaluator, similar to above, but doesn't require Java or JavaScript capability
- Visible Memory Kalculator -- provides a
growing visible memory of all values inputed or computed for use at any time later (just
click on it). Can also read text (ascii) files. (Java)
- Evaluates various
sums, cross-products, and other "building block" expressions that arise in
statistical formulas
- The Vanderbilt MathServe
Calculus Toolkit has separate calculating/graphing pages for: Factoring Polynomials,
Partial Fractions,
Polynomial Equations,
Graphs of
Functions, Graphs
of Equations, Limits,
Derivatives, Antiderivatives
(Indefinite Integrals), Definite
Integrals, Inverse
Functions, Newton's
Method, Polynomial
Interpolation, Sums,
Parametric
Equations, and Polar
Functions
- Inverse Symbolic Calculator
-- tells you where a number came from -- you type in 1.55838744, and this program tells
you that it's really the square root of 17/7.
- Calculators -- pages that look and act like a pocket
calculator...
- Plotters -- type in any algebraic function; it displays the
graph...
- Integrators -- type in any function; the computer displays the
indefinite integral function (if one exists) and/or the value of the definite integral
(area under the curve) between two endpoints...
- Interactive Programming Environments -- These pages implement
various mathematical programming languages. You can enter commands or entire programs
(type or copy/paste) into the web page, and they will be executed immediately.
- Rweb -- an interactive web-based
interface to the "R" statistical programming language (similar to S or S-plus)
- SHAZAM -- a programming environment for
econometricians, statisticians, and others who use statistical techniques. Its primary
strength is estimating and testing many types of regression models. Provides a flexible
command language and capabilities for programming procedures. Has an interface to the
GNUPLOT package for high quality graphics.
- Run arbitrary Xlisp-Stat
expressions (as long as they do not produce graphical output); with on-line Xlisp
manual and reference guide
- Mx -- a matrix algebra
interpreter and numerical optimizer for exploration of matrix algebra. Many built-in fit
fuctions for structural equation modeling and other statistical modeling. Has fitting
fuctions like those in LISREL, LISCOMP, EQS and CALIS, along with facilities for maximum
likelihood estimation of parameters from missing data structures, under normal theory.
Users can easily specify complex 'nonstandard' models, define their own fit
functions, and perform optimization subject to linear and nonlinear equality or boundary
constraints.
- Probability Integrals -- these pages take the place of a
handbook of statistical functions. They're arranged with the most
comprehensive,multi-function pages first...
- These pages contain calculations for a very wide assortment of probability
distribution functions, including Normal, Bivariate Normal, Student t, Chi-Square,
Fisher F, Bivariate Normal, Noncentral Student t, Non-central Chi-Square, Non-central
Fisher F, Poisson, Log-normal, Exponential, Beta, Gamma, Logistic, Binomial, Negative
Binomial, Multinomial, Cauchy, Gumbel, Laplace, Pareto, Weibull, Uniform (continuous and
discrete), Triangular, Geometric, and Hypergeometric:
- These pages each compute probabilities for the four most common probability
distributions:
- Normal, t,
Chi-Square, and Binomial (density and cumulative) probabilities; (When you get to the Rweb
page, scroll down to the Analysis Menu and select Probability.)
- Normal, t, F, Chi-Square,
Binomial, and Uniform probabilities and inverses
- Normal, t,
Chi-Square, Binomial; Random Digits, Number Needed to Treat
- Central and tail areas
for Normal, Student, F, Chi-Square, Binomial, and Poisson distributions (Java)
- Statistical probability distribution
functions: Normal, Student t, Chi-Square, Fisher F (JavaScript)
- Reverse computations: enter
p-value (and, if necessary, sample sizes and/or degrees of freedom); program will compute
z, t, F, Chi Square, and correlation coefficient (JavaScript)
- These pages each compute probabilities for a specific distributions:
- This page contains links to
printable copies (in Adobe Acrobat PDF format) of many statistical tables including
some for which no "calculating pages" are available
- Normal
Curve
- Critical Values for: Student t, Fisher F, Studentized
Range Statistic and Dunnett's Test, Chi-Square,
Binomial
Test, Wilcoxon
Ranked-Sums Test, Wilcoxon
Signed Ranks Test, and Correlation
Coefficient
- Converting
r to Z
- Statistical Power of: Z Test,
t-Test
for One Sample or Two Related Samples, t-Test
for Two Independent Samples, Analysis
of Variance, and Correlation
Coefficient
- Required
Sample Size for various tests
- Random Number Generators...
- Distribution/density
calculators, plotters and random number generators for a large number of distributions
- Normal, Student
t, Chi-Square, Binomial, Random Digits (Java)
- Random
integers -- generates any number of random integers, uniformly distributed between any
two limits
- Random
fractional numbers -- generates any number of random numbers, each a fraction between
0 and 1 with 8 digits after the decimal point
- Random Permutations --
generates N sets of random permutations of integers from 1 to M
- Another
random permutation generator
- Research Randomizer -- generates one or more
sets of random numbers from a specified range, with or without repeats, sorted or
unsorted.
- Block Randomizer -- assigns subjects
randomly to different groups, with multiple blocking to ensure that imbalances are kept
under control if the study is terminated prematurely
- Random
assignment of subjects to one or more groups (Java) -- three
variations:
- generates M groups of N numbers each by distributing the numbers from 1 to M*N randomly
into the M groups
- generates M blocks of N numbers each by randomly shuffling the numbers from 1 to N in
each block
- generates a subset of N numbers by random selection from a list of the numbers from 1 to
M
- Combinatorial Objects Server --
generates an incredible assortment of...
- Permutations and their restrictions
- Subsets or Combinations
- Permutations or Combinations of a Multiset
- Set Partitions
- Numerical Partitions and relatives
- Binary, rooted, free and other trees
- Necklaces, Lyndon words, DeBruijn Sequences
- Irreducible and Primitive Polynomials over GF(2)
- Ideals or Linear Extensions of a Poset
- Spanning Trees and other Subgraphs of a Graph
- Unlabelled Graphs
- Pentomino Puzzles, Polyominoes, n-Queens
- and other puzzles and Miscellanea
- Statiscope -- a
beautifully-implemented page for calculating and displaying a large number of descriptive
statistics from a set of numbers you enter (Java)
- WebStat (an integrated applet) can
generate summary statistics, as well as histograms, stem and leaf plots, boxplots,
dotplots, parallel coordinate plots, means plots, scatterplots, QQ plots, and time series
plots (Java)
- Descriptive
Sampling Statistics -- Enter up to 80 numbers; this page will calculate the mean,
variance, SD, CV, skewness and kurtosis. (JavaScript)
- Rweb -
extensive tabular and graphical descriptive summarization: mean, quartiles,
histograms, scatterplot matrices (with smoothers), QQ plots (normal and pairwise), time
series, box plots. (When you get to the Rweb page, scroll down to the Analysis
Menu and select Summary.)
- The Data Applet
provides descriptive statistics, histograms, boxplots, and scatterplots (Java)
- A variety of
descriptive statistics and a stem and leaf display
- Descriptive statistics, stem
plot, and histogram
- Detect Outliers -- this
calculator performs Grubbs' test, also called the ESD method (extreme studentized
deviate), to determine whether one of the values in the list you enter is a signficant
outlier from the rest.
- Combine
Subgroups -- calculate the mean and SD of a combination of groups from the N, mean and
SD of each group.
- Computes summary
statistics for one variable, draws a crude histogram, and sorts a list of values. Given
pairs of values, it computes the least squares regression line and Pearson correlation
coefficient.
- Basic
descriptive statistics (mean, sum of squares, variance, standard deviation, minimum,
25th percentile, median, 75th percentile, and maximum for up to 500
numbers (Java)
- Multinomial
Distributions -- Enter up to 12 values and their corresponding probabilities, and this
page will calculate Expected Value, Variance, Standard Deviation, & Coefficient of
Variation (JavaScript)
- Paired
Data Sets Statistics -- Enter up to 28 sample paired data sets, and this page will
calculate means, variances, and covariance (JavaScript)
- Histogram
-- Enter up to 80 numbers, and this page will display a histogram. (JavaScript)
- Histogram from a
set of numbers, lets you dynamically alter the interval width and see the effect
immediately (Java)
- Histogram -- type
in or upload a data set or give a URL; submit; returns a colored histogram that you can
copy from the page; also does polygons and cumulative
- Point
Pattern Analysis -- used to describe and help analyze point patterns. It consists of
14 different analysis routines for a variety of basic descriptive statistics: nearest
neighbor analysis, K-function, space-time Knox, Join-Count statistics, Global Moran’s
I and Geary’s c, general Getis-Ord’s G, local K-function, and more.
- Draw a scattergram from
{x,y} data
- Draw a 3-dimensional
scattergram from {x,y,z} data
- Generate a VRML file to view
3-dimensional (x,y,z) data. To view the resulting files requires a VRML viewer.
- Compute and plot a Kernel Density
Estimate from a set of points, using Epanechnikov, triangular, biweight or Gaussian
kernels
- Compute Poisson change-point,
that is: estimate when, in a long sequence of occurrences, the occurrence rate underwent a
sudden change
- Boxplot -- type in or
upload a data set, or give a URL; submit; returns a colored boxplot that you can copy from
the page
- Parallel Boxplot --
type in or upload a bivariate data set with a continuous variable and a group indicator;
submit; returns a colored parallel boxplots that you can copy from the page
- Q-Q Plot -- type in or
upload a data set, or give a URL; submit; returns a colored q-q plot that you can copy
from the page
- Plot up to 10 x,y data points (Java)
- Confidence Intervals...
- Single-Population Tests...
- Test a sample proportion against a
postulated population proportion
- http://department.obg.cuhk.edu.hk/ResearchSupport/Binomial_Test.asp -- whether the
number of "successes" differed from what you would have expected, based on the
number of trials and the expected probability of success
- Mean, SD, confidence
interval, etc. for a set of values
- Student t-test of a single mean (vs
specified value) from N, mean, SD
- Another
Student t-test of a single mean (vs specified value) from N, mean, SD (Java)
- Similar test of single mean vs 0
(equivalent to a paired Student t) from N, mean, SD
- Test observed vs. expected rates of
occurrence of events, based on Poisson distribution; also includes confidence
intervals and analysis of rate-ratios (such as Standardized Mortality Ratio, Morbidity
Ratio, and Comparative Mortality Figure)
- Similar to above, but used to study
the distribution of accidents and events at the individual level
- Exact confidence intervals around a
rate-ratio, using Liddell's method (also contains a number of common approximations,
for comparison) (JavaScript)
- Test observed vs expected proportions,
based on the Binomial distribution
- Binomial
Test -- whether the number of "successes" differ from what was expected
based on the number of trials and the probability of success.
- Similar to above, but deals with the
probability of a particular sample size, given an observed 'x' number positive (or white,
or car crashes) vs. an expected 'U' proportion positive
- Runs
Test for Randomness -- Enter up to 80 numbers, and this page will calculate a runs
test to see if the numbers form a random sequence (JavaScript)
- Analyze observed proportions in samples
from finite populations, based on the Hypergeometric distribution
- Test
for Normality -- Enter up to 80 numbers, and this page will test for normality based
on the Jarque-Bera statistic (JavaScript)
- Chi-Square "Goodness of Fit" test for observed vs expected
counts (NOT from Contingency Tables)...
- Measurement Errors and Error Propagation...
- Student t-test (for comparing two samples)...
- a very general Student t-test
web page -- paired or unpaired, equal- or unequal-variance, from individual
observations (which can be key-entered or copy/pasted) or summary data (N, Mean, SD or
SEM). Includes explanations and advice on carrying out this type of test.
- t-test, paired or unpaired
- t-test, paired
or unpaired
- t-test, paired or unpaired
(JavaScript)
- t-test,
paired
- t-test,
unpaired (tests for equality of variances, and performs both the equal-variance and
unequal-variance t-test)
- t-test, Unpaired (Java)
- A general 2-sample comparison
calculator, for paired, unpaired, equal-variance, obtaining its p-values from table
lookup or from resampling
- Unpaired
t-test from summary data (N, mean, SD) (Java)
- Another Unpaired t-test from summary
data
- Very general t-test program for
comparing measured quantities, observed counts, and proportions between two unpaired
samples; also produces risk ratio, odds ratio, number needed to treat, and population
analysis. (JavaScript)
- Test differences between two observed
proportions, based on the Binomial distribution
- ANOVA (Analysis of Variance) -- comparison of two or more
samples ...
- Factorial ANOVA for uncorrelated samples (extension of unpaired
Student t-test to more than 2 groups)...
- One-way factorial ANOVA, with
graphical output
- One-way factorial ANOVA for 3
Independent Samples (JavaScript)
- One-way factorial ANOVA for 4
Independent Samples (JavaScript)
- One-way factorial ANOVA from
summary data (N, mean, and SD or SEM) (JavaScript)
- Another 1-way
factorial ANOVA from summary data
- Two-way factorial ANOVA for 2
rows by 2 columns (JavaScript)
- Two-way factorial ANOVA for 2
rows by 3 columns (JavaScript)
- Two-way
factorial ANOVA for 2 rows by 2 columns, from summary data (N, mean, SD) (Java)
- Very general
n-way factorial ANOVA, with interactions, means table, interaction plots, Bonferroni
post-hoc multiple comparisons, and confidence intervals. (When you get to the Rweb
page, scroll down to the Analysis Menu and select ANOVA.)
- Repeated-Measures ANOVA for correlated samples (extension of paired
Student t-test to more than 2 matched measurements)...
- Post-Tests -- After
doing a two-way (or other) ANOVA, post tests compare individual pairs of groups. This
calculator does not perform the ANOVA calculations, but takes the output from an ANOVA
(residual means square error, degrees of freedom) performs a post test between any pairs
of cells that you select (using cell means and N's), at whatever alpha you specify.
- Tukey
LSD (Least Significant Difference), using the standard table produced by an ANOVA
- Scheffe
Least Significant Difference, using data from a standard ANOVA table and the N's for
the two groups being compared
- Non-parametric tests (use these when the data is not normally
distributed)...
- Sign test for
matched pairs
- Median test for
unmatched pairs
- Wilcoxon
Signed-Ranks test for matched pairs -- This page takes case-by-case pairs of matched
data
- Another
Wilcoxon Signed-Ranks test for matched pairs -- This page takes summarized, tabulated
data: how many cases had differences of +1, +2, +3, etc., and -1, -2, -3, etc.
- Wilcoxon
Sum-of-Ranks (Mann-Whitney) test for comparing two unmatched samples
- Kruskal-Wallis
test (non-parametric ANOVA) for 2 or more groups of unpaired data -- This page
requires that you first cross-tabulate your data into a matrix, with a row for every group
and a column for every different numeric value that any subject had; the cell of the
matrix tell how many subjects (if any) in that group had exactly that numeric value.
- Least
Significant Difference between mean ranks (post-hoc test after a significant
Kruskal-Wallis test)
- Friedman test for
comparing rankings (non-parametric)
- Two-group ordinal comparisons to assess
how probable it is that the two groups come from a single ordering, using
Wald-Wolfowitz, Randomness Test, Mann-Whitney, and Kolmogorov-Smirnov (JavaScript)
- Two-group paired comparisons,
using T-test, Wilcoxon, Signs test, and McNemar test (JavaScript)
- McNemar's test
for the paired comparison of proportions (or for matched pairs of labels)
- Comparison of proportions between two groups...
- Sequential Analysis -- each subject's data (usually paired
comparisons) is tested as it becomes available, and a decision is made to accept or to
reject the null hypothesis or to keep testing.
- WebStat (an integrated (Java) applet) can perform Z-tests and T-tests (one- and two-sample)
for population means, and Chi-square and Fisher-F tests for population variances
- Chi-Square tests...
- for 2-by-2 table (JavaScript)
- 2-by-2 table analysis
(Chi-square, sensitivity, odds ratio, relative risk, difference in proportions, number
needed to treat, etc.) with confidence intervals (JavaScript)
- 2-by-2
table analysis (Chi Square, Fisher Exact, difference in proportions, risk ratio, odds
ratio, theta, log-odds ratio, Poisson test)
- for 2-by-2 table, with
odds ratio, relative risk, etc. with confidence intervals (the results page is very
nicely formatted for printing out)
- for
2-by-N table, where the two rows represent dichotomies like lived/died,
present/absent, yes/no. This can test for a trend in the probability of an event when you
have counts of the two categories over a set of time intervals.
- for table up to about 30
cells
- for up to 10-by-10
tables. This page also has a section for comparing observed with explicitly-specified
frequencies. (JavaScript)
- for any-size table
- another
for any-size table
- another for
any-size table (When you get to the Rweb page, scroll down to the Analysis
Menu and select Two Way.)
- Exhaustive analysis of 2-by-2 tables,
with Pearson Chi-square, Likelyhood Ratio Chi-Square, Yates Chi-square, Mantel Heanszel
Chi-square, Odds Ratio, Log Odds Ratio, Yules-Q, Yules-Y, Phi-square, Pearson correlation,
and McNemar Test (JavaScript)
- Three-dimensional Tables (2x2x2)...
- Fisher Exact tests for contingency tables...
- Exact unconditional
homogeneity/independence tests for 2-by-2 tables
(said to be more powerful than the Fisher exact test!)
- Contingency table for sequenced
categories (Ordinal by Ordinal, 5-by-5 table or less) (JavaScript)
- Contingency table for sequenced categories,
5-by-2 table, with exact probability calculations (JavaScript)
- Spearman's
correlation from cross-tabbed data with sequenced row and column categories
- McNemar's
test for paired contingency tables
- Comparison of ratings or rankings by different raters...
- Chi-Square
test for equality of distributions
- Chi-Square "Goodness of Fit" test for observed vs expected
counts (NOT from Contingency Tables)...
- Straight Lines and Correlation Coefficients...
- Least squares
regression line and Pearson correlation coefficient. (Java)
- Variations on
straight-line fitting, when X and Y have error
- Least squares regression.
(nice interface)
- Linear correlation and
regression (nicely designed) (JavaScript)
- Draw a scatterplot,
and compute various statistics
- Correlation and
regression calculator -- input two sets of numbers (or upload a file); computes the
means, variances, covariance, correlation coefficient and regression coefficients; also
gives a scatterplot with the two regression lines
- The Data Applet
provides descriptive statistics, histograms, boxplots, and scatterplots (Java)
- Least squares straight
line (also allows some simple transformations), with an interesting tutorial on the topic
- Least squares
straight line, also creates a high-quality Postscript graph of your data and the fitted
line
- Least squares straight line,
allows several common types of y-value weighting (constant, proportional, or Poisson
errors); also allows you to recall recently-entered data
(for a limited time)
- Calculate partial correlation
coefficients rbc.a, rac.b, rab.c from rab,
rac, rbc (JavaScript)
- WebStat (an integrated (Java) applet) can perform simple regression analysis
- Correlation Tests...
- Spearman's rank correlation (non-parametric)...
- Correlation
test
- Significance
level corresponding to a correlation coefficient
- Minimum
significant correlation coefficient for a given sample size
- Comparison
of two correlation coefficients
- Comparison of
two or more correlation coefficients
- Comparison
of two sets of (X,Y) data to see if they are consistent with the same straight line
(tests whether the slopes are different, and whether the lines are vertically distinct)
- Biserial
and point-biserial correlation analysis
- Biserial
correlation coefficient from summary data (N, mean, SD) of the X and Y variables
- Point-biserial
correlation analysis
- Manipulation
of a correlation matrix -- you enter the N-by-N correlation matrix, the page computes
all Partial Correlation Coefficients, all Standardized Partial Regression Coefficients,
and the Multiple Correlation Coefficient for each variable.
- A versatile page for calculating the
significance of a correlation (rho<>0), significance of the difference between two
correlations, power and sample size requirements for correlations testing, and the
inter-relationships between three partial correlation coefficients.
- Sobel's test to
determine the extent to which an intermediate variable ("mediator") carries the
influence of an independent variable (predictor) on a dependent variable (outcome). (JavaScript)
- Beyond Simple 2-parameter Curve-fitting...
- Very general non-linear least
squares curve-fitter (almost any function -- even functions that are non-linear in the
parameters!). Also does least-absolute-value fitting. (JavaScript)
- Linear, parabolic, or cubic
fit, with graphics (Java) (newer version here)
- Multivariate
linear or univariate polynomial regression, with graphical output. Has a good
discussion of the relevant mathematics and computational accuracy.
- Univariate and
multiple regression, with very extensive graphical output (histograms,
scatterplots, scatterplot matrices) and residual analysis (QQ, histogram, residuals vs
dependent or predictors). Very intuitive point-and-click interface, dynamically
customized for your data. (When you get to the Rweb page, scroll down to the Analysis
Menu and select Regression.)
- Automatic Multiple Regression, (*** TEMPORARILY OFFLINE ***) automatically builds a model or
regression equation! You merely supply the dependent and independent variables and it does
the rest. It will find which variables are important enough to include in the model,
determine the proper transformation of each of those variables, then look for 2-way and
3-way interaction terms important enough to include in the model, and transform them
appropriately.
- Multiple regression, if you already have the correlation coefficient matrix between all
independent and dependent variables...
- Fit any of five families of curves
(linear, polynomial, exponential, descending exponential, Gaussian) and draw a graph (Java)
- Curve fitting, smoothing, parameter estimating,
data correlating and forecasting utility (Java)
- Logistic Regression, if the
dependent variable is restricted to two values (such as whether an event did or did not
occur) (JavaScript)
- Regression and GLM Calculator
-- performs linear, Poisson, binomial and Gamma regression, with canonical, identity,
logit, log, probit, inverse, cloglog, and sqrt link functions
- Cox Proportional Hazards Survival
Regression Analysis (JavaScript)
- A faster version of Cox
Proportional Hazards Analysis (JavaScript)
- Regression
by Prevalence -- when you have data on the number of occurrences and non-occurrences
of something over a set of time intervals. Tests whether the probability of the occurrence
shows a trend over time.
- Test Bias Assessment Program,
computes statistics to help you decide if test scores predict a criterion differently
across subgroups (Java)
- Bayes' theorem calculations --
takes prior probabilities and conditional probabilities, and calculates revised
probabilities. (great for solving certain kinds of brain teaser puzzles) (JavaScript)
- Bayesian calculations for
diagnostic tests -- computes interrelationships among true pos, true neg, false pos,
false neg, prevalence, sensitivity, specificity, predictive values, and likelihood ratios.
(JavaScript)
- Calculate the post-test probability of an
outcome (disease) from prior probability (prevalence) of the disease, and from the
sensitivity and specificity of the test (Java)
- Sequential Experimental Design for
testing the probability ratios (JavaScript)
- 2-by-2 table analysis (Chi-Square,
sensitivity, odds ratio, relative risk, etc. with confidence intervals (JavaScript)
- for 2-by-2 table, with
odds ratio, relative risk, etc. with confidence intervals (the results page is very
nicely formatted for printing out!)
- Wald's Sequential Probability Ratio's
-- for designing a sequential experiment in which a decision is made after each
observation either to accept the null hypothesis, accept the alternate hypothesis, or
acquire more observations.
Martindale's
Reference Desk - Calculators On-Line - Statistics (the grand-daddy of all
compendia of calculating web pages)
- Biostatistical Calculators...
- Number Needed to Treat
-- Explanation, examples, tables, and an interactive nomogram
- Number Needed
to Treat, also Normal, Student t, Chi-Square, Binomial, and Random Digits
- Clinical Significance
Calculator -- For two groups (control and treatment), enter the group size and
incidence rate; the page will calculate absolute and relative risk reductions, odds
ratio, and number needed to treat, along with 95% confidence intervals for each result
- Thorough analysis
of 2-by-2 table relevant to Predictions and Diagnostic Tests -- sensitivity,
specificity, prevalence, diagnostic accuracy, PPV, post-test probabilities, likelihood
ratio tests
- Calculation
of posttest probability from Likelihood Ratio and pretest probability
- Conversion
of Sensitivity and Specificity to Likelihood Ratios
- Calculator to predict the probability
of a successful outcome to lumbar disc surgery (based on a logistic model)
- LODS - Logistic Organ Dysfunction
System calculator (JavaScript)
- APACHE-II Score for acute
physiology and chronic health evaluation (JavaScript)
- Calculators for Clinical Formulas
-- A-a Gradient, Anion Gap, Body Surface Area, Body Mass Index,
Estimated Creatinine
Clearance, Fractional Excretion
of Sodium, Heart Disease
Risk, Ingested Substance
Blood Level, Pregnancy Due
Date , Serum Osmolality ,
and Weights and Measures
(converts lbs. to kgs. and F to C)
- Disparate
Impact Analysis
- Item Analysis -- for multiple choice
questionnaires
- Theoretical
Expectancy Calculator -- estimates amount of workforce improvement from implementing a
valid selection procedure in an organization. Computes institutional expectancies under
three different models.
- Investment Derivative Calculations -- A very
elaborate online calculator and real-time data retrieval system. Includes economic
regression analysis.
Check out the large number of power and sample size calculators
at the UCLA Statistics website. Many of them are included below.
- For one-group tests (comparing the sample to a specified value) or for
paired two-group tests...
- For designing surveys (sample size and confidence intervals for
proportions, based on sample size, with or without corrections for finite populations:
- For two-group tests...
- For ANOVAs and other multi-group comparisons...
- For regressions and correlation tests...
- Other power calculations...
- Links to
printable copies (in Adobe Acrobat PDF format) of many power tables including: Z Test,
t-Test
for One Sample or Two Related Samples, t-Test
for Two Independent Samples, Analysis
of Variance, Correlation
Coefficient, and Required
Sample Size for various tests
- Wald's Sequential Probability Ratio's
-- for designing a sequential experiment in which a decision is made after each
observation either to accept the null hypothesis, accept the alternate hypothesis, or
acquire more observations.
- Experimental Design...
- EDGAR --
generates experimental designs and randomizes the position of experimental treatments in
the design, so that the subsequent analysis of the data is comparatively straightforward
- Gehan/Simon Two-Stage
Designs approximating the power and significance level specified in the input.
- Find
Optimal/MiniMax Phase-II 2-stage designs, where H0: p=p0 and H1: p=p1>p0, subject
to a fixed maximum sample size, N. Finds all the designs that satisfy Type I & II
error criteria. [see Simon, Controlled Clin Trials, 10:1-10,1989]
- Compute
boundaries for a specified alpha spending function,
compute drift
given power and bound, and
compute probabilities,
all based upon the Lan-DeMets method.
Allows computation of boundaries at any time during the monitoring of a study. It is valid
for any normal test statistic with independent increments. The information time is the
ratio of accrued sample size to the total sample size for normal data.