If you get locked out of your house, it's good to know that the majority of doorknobs have built-in provisions for removal. It really shouldn't be this easy. However, if you're concerned that it's too easy, tamper-proof locksets are available.
Examine the shank of the doorknob. The mounting screws are somewhat concealed, but you can identify them by locating a tiny slot or hole in the shaft.
Insert a tool into the hole or slot. It might be the flat tip of a small screwdriver, the end of a nailset or the tip of a straightened paper clip.
Push on the tool. You should feel some resistance, similar to a spring being depressed. Push the spring as far as possible with the tool, with one hand, while pulling the doorknob off with your other hand.
Twist the tool if the doorknob resists your efforts. If it continues to resist, twist the doorknob while depressing and twisting the tool at the same time, and remove the knob.
Use a thin, flat screwdriver to pry off the round, decorative plate -- also sometimes referred to as a rose -- to reveal the lockset mounting screws.
Use a drill/driver to remove the longer mounting screws. This causes the doorknob to separate inside, and both sides can be removed from the door.
Inasmuch as doorknobs can be defeated -- smashing the knob off is another way to gain entry -- a deadbolt or mortise-bolt can be added to your door to prevent it. This type of lock penetrates deep into the jamb to slow down forced entry, often enough to stop it.
The majority of exterior doors swing inward to the home. The hinges can't be accessed to gain entry because they're on the inside.
Outswing doors are gaining ground for protection against high winds, or as a blast or fire protection garage-to-home entryway door. Outswing doors swing out to the exterior. The doorstop, on the inside of the door, stops inward movement, and reduces the chance that the door can be forced open. This places the hinge cylinders on the outside of the door. If you purchase this type of door, insist that the hinges and doorknob are tamper-proof.