In Agemba it is encouraged (but not mandatory) to take uncertainties into account when estimating effort and value. This is done by setting not only one single estimate for the effort and value, but setting both an *expected* and a *worst-case *estimate.

The *expected* estimate is what is considered as a realistic estimate with 50% certainty (it should not be confused with an optimistic best-case estimate). The *worst-case* estimate represents a realistic estimate with a 90% certainty. By considering not only the *expected* estimate, but also the *worst-case*, you force yourself to consider different scenarios and avoid the mistaken perception that estimates are certain and precise.

The uncertainty in percentage is derived as the difference between the *expected* and *worst-case *estimate, divided by the *expected *estimate. The higher the difference is compared with the *expected *estimate, the higher the uncertainty.

The *worst-case* effort estimate will always be higher than the *expected* estimate, hence the effort uncertainty can increase to more than 100%. The *worst-case *value estimate will always be lower than the *expected* value estimate, hence the value uncertainty will always be lower than 100%.

#### Accumulated Estimates

The accumulated *expected* estimate is the simple sum of the *expected* estimate of all children.

However, deriving the accumulated *worst-case* estimate is not as simple. It depends on whether you assume all the children (cards found under any major card) to be mutually independent (i.e. if one story takes more time, this does not necessarily affect the others) or if you assume the children to be mutually dependent (i.e. if one story takes more time, so will all probably). Based on this assumption, the *worst-case* estimate can be derived using either of the two methods:

- Root-sum-squared for mutually independent children – less than a simple sum of worst-case estimates:
**expected +/- √(∑(worst – expected)**^{2}) - Simple sum of worst-case estimates for mutually dependent children