False-alarm calculator
When real changes are uncommon, even a good signal produces many signals for people whose state did not change. Enter your figures to see how many. Nothing leaves your browser.
Calculate
Why it matters
With the defaults above, most signals come from people whose state did not change. That is why the State-Change Signal is a graded statement, never an alert, and why every output carries the disclosure: "At the level of one person, these signals are uncertain. In published studies they appeared before fewer than half of changes, and they appeared in about 25% of people whose state did not change."
How it works
Expected signals from people who changed = people × share with a change × share of changes that show a signal. Expected signals from people who did not change = people × (1 − share with a change) × share of those who show a signal. All figures are per person over one study period.
Questions
Is anything stored?
No. The page makes no network requests.
Can I use the result in our product?
As a planning figure. It is an expected value from the inputs you choose, not a measurement.
Keep reading
Take the next step.
Free calculator: see how many change signals come from people whose state did not change, given how common real changes are. Runs in your browser.