"A 2000 study published in the Journal of Quantitative Criminology found U.S. civilians use guns to defend from crime at least 989,883 times per year. A 1994 survey by the U.S. Centers for Disease Control and Prevention, Americans use guns to frighten away intruders who are breaking into their homes 498,000 times per year."
There is another study that shows that by having a gun in your house the odds are that you are more likely to have somebody shot in your family. But of course the gun is meant for protection. So by getting a gun in the house for protection, you increase the chances that the family you are hoping to protect will be shot by that gun.