Many surveys have a specific margin of error because all of the questions are asked of every person. For example if you ask an opinion question all of the respondents in the sample, everyone can give an opinion. The margin of error is different for different crimes and different findings in NCVS because questions are asked only of people who are victims of those crimes. There is a large margin of error around statistically rare crimes, such as rape/sexual assault. The margin of error is smaller around crimes which occur more frequently, such as property theft. Within a crime category such as violent crime, the margin of error around specific characteristics such as hospitalization may be larger than that for overall violent crime, since the estimates are based only on violent crime victims who experienced that characteristic.