Sample Size Calculator for Discovering Problems in a User Interface
Use this calculator to determine the number of users you'd need to test given the probability of detecting a problem. If the probability of detecting the problem is unknown, this calculator also allows you to estimate the problem occurrence (p) from sample data.
Graph and Calculator for Confidence Intervals for Task Times
Visualizing your task time data is an essential step in understanding its distribution and computing accurate confidence intervals. This calculator creates a dot-plot of your task times, transforms the raw data to adjust for non-normality and computes the intervals.
Confidence Interval Calculator for a Completion Rate
If you've wanted to provide a confidence interval around a small sample completion rate but just didn't have time to do the math, this calculator does the work for you.
Sample Size Calculator for a Completion Rate
Use this interactive calculator to understand how the sample size changes will affect the confidence interval around a completion rate.
Z-Score to Percentile Calculator
Look up the area under the normal curve (1 or two-sided areas) from a standard score (Z-score).
Percentile to Z-Score Calculator
Enter the area under the normal curve (a proportion between 0 & 1) and get the Z-critical value, one-sided or two-sided.
Interactive Graph of the Standard Normal Curve
Use this interactive normal curve to understand how the z-score and the area of the curve are related. Offers both one and two-sided options.
One Sample Proportion Calculator