Publisher's Synopsis
Developed by the same team that created the best-selling DOS-based program, Statistical Power Analysis, Power and Precision is a computer program for statistical power analysis and confidence intervals. A stand-alone program that may be used to find the sample size for a planned study, it offers a wide variety of important features including the ability to:
* compute power interactively by modifying elements of the study design,
* create text reports suitable for inclusion in grant applications,
* develop tables and graphs with a single click, and
* estimate precision (the width of the confidence interval) as well as power.
It also offers a host of valuable tools that provide a clear, intuitive interface. Users can easily:
* manipulate effect size, alpha, and sample size, and see immediate impact on power;
* apply Cohen's effect size conventions;
* find required sample size automatically (user may specify allocation ratio);
* take account of power and confidence interval width simultaneously;
* access an interactive guide -- Wizard -- to learn program features; and
* use a continuous summary to understand the meaning of computed data.
It's easy for a user to generate tables and graphs with just one click. One simply enters effect size and alpha and then clicks on an icon for a table or graph. The program automatically establishes the start, increment, and end-point for the sample size (based on the effect size/alpha) and generates the tables and/or graphs. If the user decides to enter more than one effect size and/or alpha, the program automatically sets up headings and subheadings and generates the corresponding tables or graphs. For example, if two values for alpha and three effect sizes are specified, the program generates a table with six columns because the sample size is also set automatically. The user, however, is still able to override any of the automatic settings. Also of importance, all of these tables and graphs may be inserted into word processing programs.
Power and Precision's extensive help system features an interactive guide, continuous summary, and a Windows 95TM style help system that includes a table of contents and an index.
