change facebook group privacy?

[Natasha]

So I got added to a group by a friend from work, for people who work at the zoo. it's a closed group. I posted something on my timeline and someone was talking to me about it at work sayin the manager and anyone else can see it including him. I said no you can't, you need to be my friend cuz I have my privacy setting to just friends. He went on his facebook and showed me my status. Wow. Really??? He's not even my friking friend!! This is a GROUP, like someone made up a group and added me to it, and now everyone in this group has access to everythin on my facebook!! WTF????? How do you change it on facebook, I tried changing post restrictions but it won't let me type in the group name at all. This is NOT a friend, it's a GROUP.
I am NOT an administrator.

[Sumukh]

If there are 150 friends in your group, you can't change privacy setting.
1) Remove your some friends, until group member reached below 150.
2) Then change privacy setting, and ask your friends to rejoin your group. This is the only one solution to solve this problem.