SamplePower®

Imagine finding the right sample size for your research in minutes and testing the possible results before you begin your study. How much time, energy and resources do you think you could save? If your sample size is too small, you could miss important research findings. If it's too large, you could waste valuable time and resources. Why waste time on unnecessary or unproductive research? Get the right sample size the first time with SamplePower.

In just a few easy steps, SamplePower helps you find the best sample size for your research. You can compare the effects of different study parameters with the flexible analytical tools. And with an interactive guide and built-in help features, you won't lose time getting up to speed. Developed by SPSS and a team of experts, including Michael Borenstein, Hannah Rothstein and Jacob Cohen, author of Statistical Power Analysis for the Behavioral Sciences, SamplePower is designed to cover:

• Means and differences in means
• Proportions and differences in proportions
• Correlation
• Oneway and factorial Analysis of Variance (ANOVA)
• Analysis of Covariance (ANCOVA)
• Regression and logistical regression
• Survival analysis
• Equivalence tests

Working with Results

• The tables can be pivoted interactively
• New methods have been added for printing and exporting the tables, including an option to export the data to Excel® or other spreadsheet programs
• Display several graphs at once in a manner that allows you to quickly assess the impact of various factors either alone or in conjunction with each other
• Graphs are linked to the pivot tables and are rebuilt automatically to reflect the structure of the tables
• Graphs may be saved in a number of formats including WMF, EMF and BMP and easily exported to programs such as Word® or PowerPoint®

Logistic Regression

• One continuous predictor or two continuous predictors
• One categorical predictor with two levels or one categorical predictor with more than two levels

Survival Analysis

• Accrual options: subjects entered prior to first study interval, subjects entered during study at constant rate, accrual varies
• Hazard rate options: constant, varies
• Attrition rate options: no attrition, constant rate, rate varies

Equivalence Tests

• Equivalence tests for means and for proportions

Perform Analysis in Minutes

SamplePower's interactive guide leads you smoothly through your analysis. The guide explains terms and takes you through the steps necessary to determine an effective sample size.

Make Informed Decisions at Every Step

SamplePower's interactive summary panel gives you concise summaries of power and precision at any point, so you can see how each decision affects your results.

See How Your Research Criteria Will Affect Power

SamplePower's tables and graphs allow you to easily assess how different combinations of research parameters (such as proposed sample size, alpha levels and duration) will affect your statistical power.

Get Accurate Guidance with Cohen's Effect Sizes

SamplePower's Tool menu provides Cohen's effect size conventions, which allow you to determine effect sizes for particular tests by simply clicking on an icon. Cohen's effect size provides users with a "rule-of-thumb" for determining otherwise ambiguous "small," "medium" and "large" effect sizes. Plug these effect sizes into the main screen to see how varying the effect size affects power or precision.

Find Sample Sizes in One Mouseclick

SamplePower's Find N tool finds the sample size for the default power setting in one click. You also have the flexibility to choose different power size settings to compare results.

• Windows 95/98/2000/NT 4.0
• SVGA monitor
• 16MB RAM
• 10MB drive space
• Pentium-class processor