In PERT analysis, a critical activity has:

Explanation: 

Critical activity:

Critical activities are those activities whose float is zero and they lie on the critical path.

Float:

Relax or delay provided to any activity is known as float.

Floats are of three types. They are as follows:

Total Float (TF):

The maximum delay or relax provided to any activity without affecting the project duration.

TF = Lj – Ei – dij

Free Float (FF):

Relax or delay provided to any activity without affecting the Earliest Start Time (EST) of the successor activity.

FF = Ej – Ei – dij

Independent Float:

Relax or delay provided to any activity without affecting the Earliest Start Time (EST) of successor activity as well as Latest Finish Time (LFT) of the predecessor activity.

IF = Ej – Li - dij

Relation among float TF ≥ FF ≥ IF

Important Points