Syntax
WEIBULL.DIST(x, alpha, beta, cumulative)
| Parameter | Description |
|---|---|
| x | Parameter of the WEIBULL.DIST function. |
| alpha | Parameter of the WEIBULL.DIST function. |
| beta | Parameter of the WEIBULL.DIST function. |
| cumulative | Parameter of the WEIBULL.DIST function. |
Examples
Warranty claim probability
Formula
=WEIBULL.DIST(365, 1.2, 1000, TRUE)
Returns ~0.2627. About 26% of products are expected to fail within a 365-day warranty period, with shape=1.2 (mildly increasing failure rate) and scale=1000 days.
Wind speed probability
Formula
=WEIBULL.DIST(15, 2.5, 10, TRUE)
Returns ~0.9453. In wind energy analysis with shape=2.5 and scale=10 m/s, about 94.5% of wind speeds are 15 m/s or less.
Maintenance planning
Formula
=1-WEIBULL.DIST(5000, 3, 7000, TRUE)
Returns ~0.8628. About 86% of machines survive past 5,000 hours with a steeply increasing failure rate (shape=3, scale=7,000).
Common Errors
#NUM!
x must be non-negative, alpha (shape) and beta (scale) must be positive.
#VALUE!
Occurs when arguments are non-numeric.
Tips
Common in reliability analysis
The Weibull distribution is the default choice for modeling product lifetimes in engineering. Shape parameter captures whether products fail early (shape < 1), randomly (shape = 1), or wear out (shape > 1).
MTTF (Mean Time To Failure)
The mean of the Weibull distribution is beta * GAMMA(1 + 1/alpha). For shape=2 and scale=1000, MTTF = 1000 * gamma(1.5) = about 886 hours.
Identical to WEIBULL
WEIBULL.DIST and WEIBULL are functionally identical. Use WEIBULL.DIST in new spreadsheets for consistency with the modern naming convention.
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