What This Calculator Measures

Estimate forecast bias using forecast mean, actual mean, and sample size.

By combining practical inputs into a structured model, this calculator helps you move from vague estimation to clear planning actions you can execute consistently.

This calculator estimates forecast bias and significance.

How to Use This Well

Enter forecast and actual means.
Add sample size and std dev.
Set bias threshold and confidence.
Review bias and t score.
Adjust model if needed.

Formula Breakdown

Bias = forecast - actual

Percent: bias / actual.

T score: bias / (std dev / sqrt(n)).

Flag: bias % vs threshold.

Worked Example

Forecast 105 vs actual 98 = bias 7.
Bias percent about 7.1%.
T score about 4.5.

Interpretation Guide

Range	Meaning	Action
Under 3%	Low.	Bias acceptable.
3-7%	Moderate.	Monitor drift.
7-12%	High.	Adjust model.
12%+	Severe.	Recalibrate.

Optimization Playbook

Reduce bias: recalibrate model.
Increase sample: improve confidence.
Track drift: monitor over time.
Adjust threshold: align with risk.

Scenario Planning

Baseline: current bias.
Lower bias: reduce forecast mean by 3.
Higher sample: add 20 samples.
Decision rule: keep bias under threshold.

Common Mistakes to Avoid

Using small sample sizes.
Ignoring variance.
Not tracking bias over time.
Setting thresholds too high.

Implementation Checklist

Collect forecast and actuals.
Compute bias.
Set threshold.
Review regularly.

Measurement Notes

Treat this calculator as a directional planning instrument. Output quality improves when your inputs are anchored to recent real data instead of one-off assumptions.

Run multiple scenarios, document what changed, and keep the decision tied to trends, not a single result snapshot.

Forecast Bias Check Calculator

Quick Facts

Your Results

Bias Plan