'Leads' quality metric
Use this metric to check the proportion of links that have no lead time, which offsets tasks backwards.
Lead time is the period that a successor task can start before its predecessor has finished. It occurs when two tasks link and overlap. Once the successor task is underway, both tasks continue in parallel. Overlapping tasks by using lead time is a way of reducing the duration of a schedule.
The lead time is illustrated by the blue arrow in the following example:
It is possible to have lead/lag at both ends of a link. If a link has lead/lag at both ends, the lead at one end of a link can affect, or even cancel out, the lag at the other end, and vice-versa. This quality metric checks the net lead time of each link, ie the lead time that results from combining the lead/lag at both ends of the link.
Lead time - or negative lag - should be avoided in a schedule as it can result in a successor task starting before the start of the predecessor. A high proportion of tasks that are offset backwards by lead time can indicate that a schedule's link logic may be prone to errors.
With the pass and fail boundaries set to 100.00%, this metric meets the requirements of CIOB stress test 2 (Negative lag) and DCMA test 2 (Leads).
Example of a link with lead time
In the following illustration, the link between Task 1 and Task 2 has 3d lead time at the start of the link. This link would fail this metric:
You can change the impact that this metric has on the weighted total result of a quality check by entering a factor by which the quality metric should be multiplied in the Weighting field. For the weighting to have any effect, a quality check must have more than one quality metric.
Pass and fail criteria
| Pass or fail? | Criteria |
|---|---|
| Pass |
A project passes this metric if the percentage of links with no lead time is greater than or equal to the pass boundary percentage.
For example, if the pass boundary was set to 100.00%, a project would pass this metric if 100% of links had no lead time. |
| Fail |
A project fails this metric if the percentage of links with no lead time is less than the fail boundary percentage.
For example, if the fail boundary was set to 100.00%, a project would fail this metric if less than 100.00% links had no lead time. |
| Neither pass nor fail | If the percentage of links with no lead time falls between the pass and fail boundary percentages, the result is neither a pass nor a fail, but somewhere in between. |
Suggested settings to meet the requirements of CIOB stress test 2 (Negative lag) and DCMA test 2 (Leads)
- Pass boundary: 100.00%. A project will pass this metric if all links have no lead time.
- Fail boundary: 100.00%. A project will fail this metric if any links have lead time.
The following table shows whether some example projects would pass or fail this metric using these settings:
| Percentage of links with no lead time | Pass or fail? |
|---|---|
| 0.00% | Fail |
| 50.00% | Fail |
| 99.99% | Fail |
| 100.00% | Pass |
Does the metric force a project to be rescheduled?
Yes. If you include this metric in a quality check, the charts and summary groups that are included in the scope of the quality check are rescheduled automatically when you execute the quality check.
Suggested actions if a project fails this metric
If a project fails this metric, select the metric in the Quality Check Results dialog and click Show Failing Tasks to view the links that have failed the metric, together with the tasks at either end of the links.
Examine the links to determine whether it is appropriate for them to have lead time. If a link has inappropriate lead time, edit the link and remove the lead time.