Enter Cell Means
Use four cell means from a 2×2 design. The calculator estimates simple effects, main effects, and the interaction effect.
Example Data Table
| Factor A Group | Level 1 | Level 2 |
|---|---|---|
| Control | 22 | 28 |
| Treatment | 31 | 45 |
This table shows the four cell means used by the calculator. Each value represents the outcome average for one specific combination.
Plotly Graph
Parallel lines suggest no interaction. Nonparallel lines indicate that the treatment effect depends on the second factor level.
Formula Used
For a 2×2 layout, let the cell means be:
- M00 = first group at first level
- M10 = second group at first level
- M01 = first group at second level
- M11 = second group at second level
Simple Effect at first level: M10 − M00
Simple Effect at second level: M11 − M01
Interaction Effect: (M11 − M01) − (M10 − M00)
Main Effect of Treatment: [(M10 + M11) / 2] − [(M00 + M01) / 2]
Main Effect of Factor B: [(M01 + M11) / 2] − [(M00 + M10) / 2]
An interaction exists when the change caused by one factor differs across the levels of the other factor.
How to Use This Calculator
- Enter labels for the two treatment groups and both levels.
- Provide the four cell means from your 2×2 design.
- Click the calculate button to view interaction results.
- Review simple effects, main effects, percentages, and interpretation.
- Inspect the graph to see whether lines are parallel.
- Use the CSV or PDF options to export your results.
Frequently Asked Questions
1. What does the interaction effect mean?
The interaction effect shows whether the treatment difference changes across the second factor’s levels. If the gap between groups shifts from one level to another, an interaction is present.
2. What does a zero interaction effect indicate?
A zero value indicates equal simple effects across both levels. In a line graph, this usually appears as parallel lines, meaning the treatment effect stays consistent.
3. Can I use raw data instead of means?
This version is designed for cell means. If you have raw observations, compute the mean for each cell first, then enter those four values.
4. Why are simple effects useful?
Simple effects show how large the treatment difference is within each level of the second factor. They make interaction patterns easier to understand and explain.
5. What if the graph lines cross?
Crossing lines usually indicate a strong interaction. It suggests the direction or size of the treatment effect changes depending on the second factor level.
6. Does this calculator perform significance testing?
No. It estimates effect sizes from cell means only. Statistical significance requires additional information, such as sample sizes, variance, and an ANOVA model.
7. When should I export CSV or PDF?
Use CSV for spreadsheet work, reports, or further analysis. Use PDF when you need a print-friendly summary for sharing, documentation, or presentations.
8. Is this limited to a 2×2 design?
Yes. This page focuses on a simple two-factor, two-level structure. Larger factorial designs need more cells and a broader calculation framework.