A little while ago, I was listening to the radio show "A way with words" (episode: Upstairs basement 9 June 2014) when I heard the host Grant saying that phrase. I had to do a little research and confirmed that "another" can only be used with singular nouns and not with plural nouns. People is a plural noun.
If you conduct a COCA search, you'll get 74 hits as of this writing from different register sources. I know that people can have the meaning of "all the men, women and children who live in a particular country" as in "The French are known as a food-loving people.". Because of time constraints I cannot go any further, and curiosity makes me want to know now and not later whether this usage is informal. Is it so?
Another as a determiner (From Cambridge's website)
We use another with singular nouns:
- Would you like another cup of coffee?
- You’ve met Linda, but I have another sister who you haven’t met, called Margaret.
- I don’t like this place. Is there another café around here we could go to? (alternative or different)
Another: typical errors - Another is singular. We don’t use it with plural nouns:
Other interesting places to visit include the old harbour and the castle.
Another interesting places to visit...