Power and Precision
Power and Precision
——统计幕数及可靠区间分析
Power and Precision is a stand-alone statistical power analysis software package that is used for the calculation of a sample size for a planned study. The program features an unusually clear interface, and many tools to assist the user in developing an understanding of power analysis. It incorporates the ability to create tables, graphs, and reports with a single click.
Work interactively!
Interactive guide walks you through all the steps in the power analysis
Modify any element in the study and immediately see the impact on power
Use a wide array of tools to visualize the effect size and to understand the impact of alpha, effect size, and sample size
Create A Report with a Single Click!
The program generates a lucid, comprehensive report that explains the study design, assumptions, and power.
The report serves as a teaching tool and may also be used in the statistics section of a study proposal or grant application
Export to Word™ or other word processing program.
Create Tables and Graphs with a Single Click!
Get the big picture in just seconds! Use graphs to quickly evaluate any number of options for study design.
Export to Word™, Excel™, PowerPoint™ and other programs.
Include the graphs in your presentation or grant application to justify your selection of a sample size.
The program features an unusually clear interface, and many tools to assist the user in developing an understanding of power analysis. It incorporates the ability to create tables, graphs, and reports with a single click. It includes a number of features that are helpful for teaching power analysis, and others that allow the researcher to explain and justify the selection of a sample size for grant applications.
This statistical program is currently in use in more than 8,000 institutions. Our clients include several thousand universities, numerous consulting firms and research institutes, many major pharmaceutical companies, various government agencies including the FDA and the CDC, as well as numerous other entities both in the U.S. and abroad.
The program is shipped with a 300 page manual that includes a comprehensive introduction to power analysis as well as worked examples and algorithms for all procedures.
Working With Results
Tables
Print directly
Copy to clipboard as data and insert into Microsoft Excel® or other spreadsheet New!
Copy to clipboard as a bitmap and insert into Microsoft Word ® or other word processing program
Graphs
Print directly
Copy to clipboard as data and insert into Microsoft Word® or other word processing program
Export as bitmap (BMP), Windows Metafile (WMF) or Windows enhanced Metafile (EMF) and insert into Microsoft Word®, PowerPoint® or other programs New!
Reports
Save as RTF file or copy to clipboard and insert into Word ® or other word processing programs.
Stored Scenarios (Sensitivity analysis)
Print directly
Copy to clipboard as data and insert into Microsoft Excel® or other spreadsheet New!
Copy to clipboard as a bitmap and insert into Microsoft Word® or other word processing program
Tables and graphs
Pivot the tables interactively New!
Display several graphs at once to assess the impact of factors in isolation or in combination with each other. New!
Graphs are linked to the tables - Drag and drop columns in table, and the graphs are updated as well. New!
Graphs can be saved as BMP, WMF, EMF files and easily exported to Word, PowerPoint, and other programs. New!
Tabulate and graph precision (confidence interval) and standard error as well as power for proportions and means.
Tools and Features
Find the sample size for a given level of power
Assign subjects to groups using allocation ratio
Store and restore any set of parameters
Apply Cohen’s effect size conventions
Store scenarios to list (sensitivity analysis)
Customize the spin control for sample size
Customize data entry
Set alpha and tails, link to confidence interval
Customize the number of decimals displayed
Display power using digits or bar graph
Statistical Procedures
t-tests and z-tests
One group against a null of zero
One group against a user-specified null
Paired/change against a null of zero
Paired/change against a user-specified null
Two independent groups, enter difference score
Two independent groups, enter mean for each group
Proportions
One group against a null of 50%
One group against a user-specified null
Two independent groups (Eight computational options for power including Fisher exact test. Indices include risk difference, relative risk, and odds ratio).
McNemar test of paired proportions
KxC test of independent proportions*
Sign tests
Correlations
One group against a null of zero
One group against a user-specified null*
Two groups*
Analysis of variance/covariance
One way analysis of variance/covariance
Two way fixed effects factorial anova/ancova
Three way fixed effects anova/ancova
Multiple hierarchical linear regression
Templates for common designs including covariates followed by main effects; main effects followed by interactions; dummy-coded variables; and polynomial regression
Customize the design with up to 10 sets of variables and up to 99 variables per set
Computes power for the increment to R-squared at each step and also for the cumulative R-squared at each step
Compute power for sequential sets combined
Logistic regression* New!
One continuous covariate
Two continuous covariates, one partialled
Two continuous covariates combined
One categorical covariate up to 5 levels
Survival analysis* New!
Accrual options - Prior to study, constant rate, or varies
Hazard - Constant rate or varies
Attrition (Drop-outs) - None, constant rate, or varies
Equivalence tests New!
Proportions*
Means
General Case
Compute power using the non-central t distribution, non-central F, or non-central chi-square distributions
Power, confidence intervals, tolerance intervals
Compute power for all procedures
Compute precision (expected width of confidence intervals) for t-tests, z-tests, one sample proportions, two independent sample proportions, and one sample correlation
Compute tolerance intervals for t-tests
Computational Algorithms
Includes exact algorithms for all procedures except where noted by (*).
Help and Technical Support
Interactive guide
Continuous summary
Tip of the day
Windows Help System including Table of Contents, Index, Step-by-Step Help
Technical support by e-mail or phone
Printed manual
The printed manual explains the logic and proper application of power analysis. It also includes worked examples for each statistical procedure, and details for all algorithms An extensive Help system provides step-by step instructions for each procedure.
Developed by a Team of Experts
Michael Borenstein, Jacob Cohen, Hannah Rothstein, David Schoenfeld, Jesse Berlin, Ed Lakatos