Final answer:
To collect Performance Analytics data in ServiceNow, the HR Administrator group needs to be granted the Performance Analytics Data Collector [pa_data_collector] role, which specifically allows for data collection within the Performance Analytics module.
Step-by-step explanation:
If the HR Administrator group has been tasked with collecting Performance Analytics data on the ServiceNow platform, the additional role that should be granted to the group is Performance Analytics Data Collector [pa_data_collector]. The pa_data_collector role is specifically designed to allow users to collect and input data into the Performance Analytics engine. The other roles listed have different levels of access and privileges which are not specifically focused on the data collection aspect of Performance Analytics. For instance, the pa_admin has broader administrative rights over Performance Analytics, the pa_threshold_admin manages thresholds and indicators, and the admin role grants full system administration privileges.