Hi Cindy,
PDT is not maintained at material group level.
PDT is maintained in the material master (view "MRP 2") when you enter a non-vendor-specific planned delivery time.
It could also be maintained in the Purchasing Info Record when you enter a vendor-specific PDT.
The system will give priority to the PDT of the Info Record.. in case the system does not determine an info record, then it will consider the PDT of the Material Master.
You will need to identify the materials of a specific material group and then assign a PDT for those materials in the material master or info record.
Kind Regards,
Mariano