use the command below:
(192.168.1.3) #show aaa authentication-server radius statistics
RADIUS Server Statistics
------------------------
Server Acct Rq Raw Rq PAP Rq CHAP Rq MSCHAP Rq MSCHAPv2 Rq Mismatch Rsp Bad Auth Acc Rej Acct Rsp Chal Ukn Rsp Tmout AvgRspTm Tot Rq Tot Rsp Rd Err Uptime SEQ
------ ------- ------ ------ ------- --------- ----------- ------------ -------- --- --- -------- ---- ------- ----- -------- ------ ------- ------ ------ ---
192.168.1.25 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 7:23:46 0/0
cppm-192.168.1.32 0 4867 0 0 0 0 0 0 725 0 0 4142 0 91 13 4867 4867 0 7:23:46 255/255
*AvgRspTm is in msec, Uptime is in d:h:m, SEQ is in Total/Free
Orphaned requests = 0
AvgRspTM is the average response time in milliseconds...