Is it a lower F-Stop Setting for a blurry background?

When your lens focuses on a subject, the rule of thumb is that there is an area 1/3 in front of the focus point and 2/3 behind the focus point that is also in focus. The old film lenses would show you that distant in feet on the barrel of the lens (today's auto focus lenses do not unfortunately). As you open up the lens (moving from say f/11 to f/4) the area in focus in front of and behind the subject gets smaller. Now as far as your question goes, if the subject is fairly close to the lens the effect of blurred background will be more noticeable as you open the lens. However as the subject moves farther and farther away, the 2/3 behind in focus gradually drifts towards infinity so no matter what f/stop you choose, the background will stay in focus if the subject is also in focus.