Study Design and Power Analysis Planner

Browser-based planning tool for HCI studies with a focus on a-priori power analysis, sample-size planning, study-design guidance, and placeholder data generation.

What the tool does

The planner lets users:

• define independent variables (IVs) and dependent variables (DVs)
• build between-subject, within-subject, mixed, t-test, and regression scenarios
• estimate effect sizes from means and pooled standard deviation or direct effect-size input
• compute a-priori sample sizes directly in JavaScript in the browser
• inspect Minimum N and design-aligned Required N
• choose a controlling effect for ANOVA-based sample-size recommendations
• view formulas, charts, and placeholder data tables for reporting and analysis preparation

Supported analyses

The current browser engine focuses on:

• one-way between ANOVA
• one-way repeated-measures ANOVA
• mixed ANOVA interaction (within-between interaction)
• general factorial ANOVA overview rows
• independent two-sample t-tests
• paired t-tests
• multiple regression

Exact power formulas

The JavaScript power engine now uses explicit noncentral F and noncentral t based calculations for the primary a-priori cases instead of relying only on broad heuristics.

Implemented exact paths include:

• estimateSampleSizeOneWayBetweenExact(...)
• estimatePowerOneWayBetweenExact(...)
• estimateSampleSizeOneWayWithinExact(...)
• estimatePowerOneWayWithinExact(...)
• estimateSampleSizeMixedInteractionExact(...)
• estimatePowerMixedInteractionExact(...)

These functions are exported through:

• window.StudyPowerEngine
• window.PowerEngine

Sample-size concepts

The UI distinguishes between:

• Minimum N: the smallest sample size that reaches the target power for the selected effect
• Required N: the smallest design-compatible sample size after rounding to the current design sequence multiple

The analysis view is driven by the Required N of the currently selected controlling effect.

Project structure

• index.html: static application shell
• _js/planner-app.js: UI flow, rendering, study-design handling, chart setup
• _js/power-engine.js: browser-side statistical engine
• _css/style.css: styling and responsive layout

Local usage

No build step is required. Open index.html in a browser or serve the folder with a lightweight static server.

Notes for contributors

• The UI is intentionally dependency-light.
• Please preserve the browser API surface used by the site, especially window.StudyPowerEngine.

Citation

@inproceedings{10.1145/3544549.3585890,
	author = {Schwind, Valentin and Resch, Stefan and Sehrt, Jessica},
	title = {The HCI User Studies Toolkit: Supporting Study Designing and Planning for Undergraduates and Novice Researchers in Human-Computer Interaction},
	year = {2023},
	isbn = {9781450394222},
	publisher = {Association for Computing Machinery},
	address = {New York, NY, USA},
	url = {https://doi.org/10.1145/3544549.3585890},
	doi = {10.1145/3544549.3585890},
	booktitle = {Extended Abstracts of the 2023 CHI Conference on Human Factors in Computing Systems},
	articleno = {272},
	numpages = {7},
	keywords = {HCI Toolkit, Organization, Study Design Planning, User Studies},
	location = {Hamburg, Germany},
	series = {CHI EA '23}
}