Sudo error

I want give a user "sar" permission, so I modify the sudoers file: unix1 is the group for users can use sar command

Cmnd_Alias RUN_SAR = /usr/sbin/sar

User_Alias UNIX1_USERS = %unix1

UNIX1_USERS ALL = NOPASSWD:RUN_SAR

However, when I run sar command, it shows:

$ sar 1 4
sar: The file access permissions do not allow the specified action.

sudo /usr/sbin/sar 1 4

Though, perhaps the use of parameters might still produce errors... Check your sudo manpages for more info...
Regards.