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In this article
EXPON.DIST gives the chance the wait until the next event is under a given time.
Syntax
=EXPON.DIST(x, lambda, cumulative)| Argument | What it means |
|---|---|
lambda |
Events per unit time. |
Examples
Example 1
=EXPON.DIST(1, 3, TRUE)About 95%: the next call arrives within a minute at 3 calls/minute.
EXPON.DIST in practice
Where you will use it
- Chance a machine fails within T hours
- Wait time between customer arrivals
- Reliability planning
Worked example
| Hours | Rate per hour | Formula | Result |
|---|---|---|---|
| 10 | 0.05 | =ROUND(EXPON.DIST(A2,B2,TRUE),4) | 0.3935 |
| 24 | 0.05 | =ROUND(EXPON.DIST(A3,B3,TRUE),4) | 0.6988 |
| 2 | 0.5 | =ROUND(EXPON.DIST(A4,B4,TRUE),4) | 0.6321 |
Results calculated in Excel.
Mistakes people make
| Mistake | What to do instead |
|---|---|
| Rate vs mean | Rate = 1/mean time between events |
| Cumulative flag | TRUE gives probability within the time |
Related functions
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📎 Practice files for this article
- 📗Practice workbook: Statistics advanced33 tasks on realistic sales data — type your formula, the Check column turns green when it is right. Answers sheet included.⬇ XLSX · 36 KB
Free to use for learning. Files with macros (.bas) are plain text — import them with Alt+F11 → File → Import File, and always test on a copy.
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