When the certainty grabbers are at –Infinity and +Infinity, the certainty range includes every forecast value regardless of the size of the display range.
Crystal Ball compares the number of values in the certainty range with the number of values in the entire range to calculate the certainty level for the forecast. The example in Figure 22, Forecast chart shows a certainty level of 100% since the default certainty range includes all possible values. By default, Crystal Ball calculates the certainty level based on the entire range of forecast values.
The certainty level is one of Crystal Ball’s key statistics because it shows the probability of achieving the values within a specific range. With Crystal Ball, you can determine the certainty level for specific value ranges either by moving the certainty grabbers on the forecast chart or typing the certainty minimum and maximum in the fields. You can also type a certainty level in the certainty field to get a certainty range centered around the median.
When you move the certainty grabbers, the certainty range changes and Crystal Ball recalculates the certainty level. When you type minimum and maximum values, Crystal Ball moves the certainty grabbers for you and recalculates the certainty level. When you type the certainty level in the certainty field, Crystal Ball moves the certainty grabbers to show you the value range for the certainty level you specified.
The following sections describe how to adjust and analyze certainty levels in Crystal Ball: