Log-normal distribution
Positive durations formed by several multiplicative effects, producing a right tail.
On this page
Shape previewPositive and right-skewed; the median marks the middle of the distribution.
Relative densityDuration (seconds)
- median
- 8 s
- Use when
- Positive durations formed by several multiplicative effects, producing a right tail.
- Avoid when
- Variation is approximately symmetric around the mean.
- Support
- Positive values with a potentially long right tail.
- Parameters
- Median and sigma; larger sigma produces greater multiplicative spread and a heavier right tail.
- Common mistake
- Treating sigma like a standard deviation measured in the original time units.
- Example
- Repair times where most jobs are moderate but complicated cases can take much longer.