When the Probability Calculator seems to misbehave, the cause is usually one of two things: something stopped the tool from running, or it ran but the result is not usable. This guide starts with the fastest checks, then walks through the common problems and exact fixes.
Quick Checks First
- Refresh the page - a stalled session is the most common cause of nothing happening.
- Confirm the input is not empty and actually contains what you meant to submit.
- Try the smallest possible input; if that works, the issue is size, not the tool.
- Turn off browser extensions that block scripts, then reload and test again.
- Update or switch browsers if the problem repeats across sessions.
Common Problems and How to Fix Them
My union probability exceeds 1.
Overlapping events were counted twice - subtract the intersection to correct it.
The intersection looks too small.
For independent events you multiply the chances; linked events need conditional probability instead.
My result is larger than both inputs.
That is normal for a union - combining alternatives can never be less likely than either event alone.
The events in my problem are not independent.
The simple product rule assumes no influence between events, so supply a conditional chance for linked ones.
I want odds, not probability.
Convert with odds = p / (1 - p), so a probability of 0.8 becomes 4 to 1.
Results look rounded oddly.
The display shows a few decimal places - keep more digits in your own working before rounding for presentation.
When It Works but the Output Is Poor
If the tool runs fine but the result misses, the problem is almost always the brief, not the software:
- Adding probabilities that overlap
- Assuming independence without checking
- Treating dependent events as independent
- Reading 0.8 as 0.8 percent
How to Stop It Happening Next Time
- Keep a saved prompt template for every task you repeat.
- Change one setting per generation so causes stay obvious.
- Run a two-minute sanity test with known input after any update.
- Note every failure and its fix; a short troubleshooting log pays for itself.
Still Stuck?
Reproduce the problem with the smallest possible input and note the exact steps that triggered it. A one-line description of what you did, what you expected and what happened is enough to get a precise answer from support or a colleague.
Frequently Asked Questions
What do union and intersection mean?
Union is the chance that either event happens, while intersection is the chance that both happen together.
Does it handle dependent events?
The built-in combination rules assume independence, so linked events need a conditional probability supplied by you.
How do I enter a percentage?
Use decimals between 0 and 1 - a value of 0.25 means a 25 percent chance.
Is my input stored?
No - calculations run in your browser with nothing saved.
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