PASS

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. Interactive guide walks you through all the steps in the power analysis. Use a wide array of tools to visualize the effect size and to understand the impact of alpha, effect size, and sample size. The report serves as a teaching tool and may also be used in the statistics section of a study proposal or grant application. Include the graphs in your presentation or grant application to justify your selection of a sample size.

ABTestly is an A/B testing platform for teams that ship experiments in code rather than through a visual editor. You write each variation as real JavaScript and CSS. Experiments live in your repository and go through the same review as any other change. The runtime is about 31 KB gzipped, and the page is held until the variation is applied, so visitors do not see the control flash first. Assignment, exposure and conversion are recorded as three separate events on an exact ledger rather than one inferred number, so results stay auditable. Confidence intervals are shown with the sample size, no winner is declared before significance, and sample ratio mismatch is detected and flagged. Three statistics engines: frequentist on every plan, sequential and Bayesian from Pro upwards. Also a speed guardrail comparing p75 LCP against control. Pricing is published: $99 a month at 50,000 tracked users, $249 at 200,000, $549 at 500,000, with a 14-day trial on monthly plans.