Leads and Lags

Correct Answer: A 5-day lead on a Finish-to-Start relationship

When activities overlap with Activity B starting before Activity A ends, the correct way to show this in a network diagram is using a Finish-to-Start (FS) relationship with a lead time. In this case, since Activity B starts 5 days before Activity A finishes, we apply a 5-day lead to the Finish-to-Start relationship. A lead is shown as a negative lag in scheduling notation, allowing the successor activity to start before its predecessor finishes. Other options are incorrect because: - Using a Start-to-Start relationship with positive lag would incorrectly define when Activity B begins relative to Activity A's start, not its finish - A Start-to-Finish relationship would create an illogical sequence where the successor would need to finish before the predecessor starts - Adding a delay parameter would push Activity B later, not earlier, which is the opposite of what we need for an overlap

Correct Answer: To express that Activity Z must start 5 days before Activity Y finishes

A negative lag (or lead) in a finish-to-start relationship indicates that the successor activity can begin before the predecessor activity is completed. In this case, the negative 5-day lag means Activity Z (successor) can start 5 days before Activity Y (predecessor) finishes. This is a common scheduling technique used to fast-track or compress the project schedule when activities can overlap. The other answers are incorrect because: - Starting 5 days after Activity Y starts plus a buffer period would be a different type of relationship and would be expressed differently - A mandatory preparation phase would be shown as a separate activity in the network diagram - A constant 5-day separation would require a different type of relationship (Start-to-Start or Finish-to-Finish) and would be expressed differently in the network diagram

Correct Answer: Lead-time value of -80%

In PDM (Precedence Diagramming Method), when an activity can start only after another activity has reached a certain percentage of completion, we use a Lead-time percentage value. When Activity B can start after Activity A is 20% complete, this means B can start 80% before Activity A finishes (since 100% - 20% = 80%). This is expressed as a negative lead time of -80%. A lead time is shown as a negative value because it reduces the waiting time between activities. The other options are incorrect because: - A positive lag would delay the start of Activity B until after A is complete - A discretionary dependency relates to preferred logic, not percentage completion - A mandatory dependency with completion overlap doesn't properly express the 20% completion requirement