Yup. I keeps things from getting out, but also can help from things getting in. I do patient transportation at a hospital, and sometimes we have to wear PPE before going in a room. Not just to keep the patient safe, but also ourselves.
Is there studies that determined how the effectiveness of masks degraded when improperly worn?
That'd be interesting to read. My gut feeling is to say if you wear it over your nose and mouth, even incorrectly, it is still better than nothing. But sometimes, intuition is wrong.
And someone got angry with me when I said that only masks was a half measure and if you're thinking you might be around contagious people, you should also wear a face shield to protect against accidental spits or other moister getting in your eyes.