Is it possible to use AND with a range of cells?

AND OK.pdf

What I would like to achieve is this:

D1 = "ok" if A1 to A9 are all "ok"
Values on column A can be "ok," "not ok"

I can use AND but the problem is, if I have to check 20 cells, my formula will be really long. I was wondering if somebody can help me shorten my formula.

Thank you very much!