what is the self report survey? What is the National Crime Victimization Survery?

Answer 1

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National Crime Victimization Survey Resource Guide
About NCVS
Using the NCVS Resource Guide
NCVS Data (Data Content, Hierarchical v. Incident-level files)
File Structure
Methodological Issues in the Measurement of Crime
Calculating Crime Rates (Data Year v. Collection Year, Calculating Crime Rates (Steps), Sample Code)
NCVS Crime Counts and Rates Tables
NCVS Redesign Information (About the Redesign, Break in Series, Longitudinal Comparisons, NCVS Redesign-Related Bureau of Justice Publications)
Accuracy of Estimates (Sampling and Nonsampling Error, Standard Error Computation, Weighting Information)
Online Analysis of NCVS Data (Run frequency or crosstabulation, Comparison of means/correlations, Download a customized subset of variables/cases)
Using the Interactive Codebuilder (Create SPSS code for subsetting and analysis)
Other NCVS Resources
Download NCVS Data
About NCVS
The National Crime Victimization Survey (NCVS) series, previously called the National Crime Survey (NCS), has been collecting data on personal and household victimization since 1973. An ongoing survey of a nationally representative sample of residential addresses, the NCVS is the primary source of information on the characteristics of criminal victimization and on the number and types of crimes not reported to law enforcement authorities. It provides the largest national forum for victims to describe the impact of crime and characteristics of violent offenders. Twice each year, data are obtained from a nationally representative sample of roughly 49,000 households comprising about 100,000 persons on the frequency, characteristics, and consequences of criminal victimization in the United States. The survey is administered by the U.S. Census Bureau (under the U.S. Department of Commerce) on behalf of the Bureau of Justice Statistics (under the U.S. Department of Justice).

The NCVS was designed with four primary objectives: (1) to develop detailed information about the victims and consequences of crime, (2) to estimate the number and types of crimes not reported to the police, (3) to provide uniform measures of selected types of crimes, and (4) to permit comparisons over time and types of areas. The survey categorizes crimes as "personal" or "property." Personal crimes cover rape and sexual attack, robbery, aggravated and simple assault, and purse-snatching/pocket-picking, while property crimes cover burglary, theft, motor vehicle theft, and vandalism. The data from the NCVS survey are particularly useful for calculating crime rates, both aggregated and disaggregated, and for determining changes in crime rates from year to year.

Using the Resource Guide
The National Archive of Criminal Justice Data (NACJD), a part of the Inter-University Consortium for Political and Social Research (ICPSR) at the University of Michigan, designed this Resource Guide for World Wide Web users to learn about the NCVS dataset and to connect to other NCVS information sources.

With this guide, first time users or experienced analysts can:

Find general information about NCVS.
Connect to other NCVS - related sites.
Access and learn about NCVS Programming Files.

Download NCVS data files, codebook, and SPSS or SAS data definition statement files.
NCVS Data
The data include type of crime, month, time, and location of the crime, relationship between victim and offender, characteristics of the offender, self-protective actions taken by the victim during the incident and results of those actions, consequences of the victimization, type of property lost, whether the crime was reported to the police and reasons for reporting or not reporting, and offender use of weapons, drugs, and alcohol. Basic demographic information, such as age, race, gender, and income, is also collected to enable analysis of crime by various subpopulations.

Each year of the NCVS is comprised of a hierarchical, or "full," file and various incident-level files. The hierarchical file contains all of the incidents reported as occurring in a given year. Due to the timing of sample interviews, it will also include incidents occurring in the year prior to and the year subsequent to the given year. Incident-level files are prepared from the hierarchical file and are easier to work with. Generally three incident-level files are available: single year incident-level file, concatenated multi-year incident-level file (1992-present), and concatenated multi-year rape subset file (1992-present). Unlike the hierarchical file, the single year incident-level files are "bounded" to include only incidents occurring in the given year. The online version of the NCVS includes the concatenated multi-year incident-level file. Users can easily select a particular year and crime type of interest.

File Structure
Data from the National Crime Victimization Surveys (NCVS) are available from the ICPSR in a variety of forms designed to facilitate their accessibility and analytical use. These include the full data collection, which is stored as a hierarchically structured data file, and a variety of smaller extract files. The organization and use of these files is described below.

Unlike most data files which are stored in a rectangular format (also know as "flat" format) with fixed record lengths, the structured file is organized into a hierarchical format which corresponds to variations in household composition and in the occurrence of incidents of victimization. Hierarchical datasets have varying record lengths, and each record is stored sequentially in the data file. Hierarchical storage greatly reduces the size and space needed to store and process the data. For the NCVS-92-present hierarchical data files, there are four types of records: 1) address ID record, 2) household record, 3) person record, and 4) incident record. The address ID and household records contain information about the household as reported by the respondent and characteristics of the surrounding area as computed by the Bureau of the Census. The person record contains information about each household member age 12 years and older as reported by that person or proxy, with one record for each qualifying individual. Finally, the incident record contains information drawn from the incident report completed for each household incident or person incident mentioned during the interview.

To illustrate, a typical cluster of housing units might contain four households, each with varying numbers of inhabitants some of whom report victimizations. The records for such a cluster might look as follows:

RECORD
RECORD TYPE OR CONTENTS

First Household

1
Address ID #1

2
Household #1

3
Person #1 of Household #1

4
Incident #1 for Person #1 of Household #1

Second Household

5
Address ID #2

6
Household #2

7
Person #1 of Household #2

8
Person #2 of Household #2

9
Incident #1 for Person #2 of Household #2

10
Incident #2 for Person #2 of Household #2

Third Household

11
Address ID #3

12
Household #3

13
Person #1 of Household #3

14
Person #2 of Household #3

15
Incident #1 for Person #2 of Household #3

16
Incident #2 for Person #2 of Household #3

17
Incident #3 for Person #2 of Household #3

18
Person #3 of Household #3

Fourth Household

19
Address ID #4

20
Household #4

21
Person #1 of Household #4

22
Incident #1 for Person #1 of Household #4

23
Incident #2 for Person #1 of Household #4

24
Person #2 of Household #4


With four different types of records, twenty-four in all, this may seem like a very complex structure. However, storing the data in this way allows for much greater technical efficiency.

If these data were stored in a rectangular fixed format ("flat") data file, a number of problems would have to be dealt with. For example, a household-level dataset may be constructed where the maximum number of persons is two and the maximum number of incidents reported are two per person. Four hypothetical household records from this data - each representing one household - consists of the following: one record with a single person and no incidents reported; a second record with two persons and no incidents reported; a third record with two persons where person one reports one incident; and a fourth record with two persons where person two reports two incidents. A rectangular data structure would require that the fixed record length be large enough to contain all combinations of persons and incidents. In this example, the record length would require one place for the address ID-level data, one place for the household-level data, two places for the person-level data (one place for each person), and two places per person for the incident-level data. Most of this space would consist of missing data padding demanded by the fixed record length.

Assuming that each record type is approximately equal in size, approximately 50% of this small and uncomplicated file would consist of missing data padding. A hierarchical file avoids this wasted space by recording the data in fixed record lengths but only for existing data recorded from the interviews, thus utilizing space more efficiently.

SAS and SPSS program files provide the information needed to describe the composition of the varying record lengths and create datasets or subsets suitable for analysis. To access the appropriate information from a sequenced file, the underlying logic of the data structure must be understood. Using SAS and SPSS software, the four record types found in the NCVS-92-present full hierarchical file are then linked together in a hierarchical pattern, where the address ID record forms the basic building block for the file. The household, person, and incident records are then linked in a subordinate way to "root" this group.

As a link is followed down from the root, the relationship is always one to many. In the NCVS-92-present data, each occurrence of a household will have associated with it any number of persons, and each occurrence of a person will have any number of incidents associated with it. In no case will a person-level record occur without a household or with additional households superordinate to it. The same is true for incidents vis-a-vis persons.

Because of the hierarchical nature of the NCVS-92-present data files, identification or "linkage" variables have been added to each record type. These identification variables can be combined to create a link from the root to the lowest level in the hierarchy, which in the case of these hierarchical files is the incident record. The creation of links between the various record types is crucial when generating various file structures, ensuring accurate retrieval, and permitting file updating. The following is a list of the identification variables found in the NCVS-92-present full hierarchical data files:

LINKAGE VARIABLES FOR RECORD TYPE 1
Identification Variable
Description

V1002
ICPSR HOUSEHOLD IDENTIFICATION NUMBER

V1003
YEAR AND QUARTER IDENTIFICATION

V1004
SAMPLE NUMBER

V1005
SCRAMBLED CONTROL NUMBER

V1006
HOUSEHOLD NUMBER

V1007
LAST TWO DIGITS OF SCRAMBLED CONTROL NO.

V1008
PANEL AND ROTATION GROUP


LINKAGE VARIABLES FOR RECORD TYPE 2
Identification Variable
Description

V2002
ICPSR HOUSEHOLD IDENTIFICATION NUMBER

V2003
YEAR AND QUARTER IDENTIFICATION

V2004
SAMPLE NUMBER

V2005
SCRAMBLED CONTROL NUMBER

V2006
HOUSEHOLD NUMBER

V2007
LAST TWO DIGITS OF SCRAMBLED CONTROL NO.

V2008
PANEL AND ROTATION GROUP


LINKAGE VARIABLES FOR RECORD TYPE 3
Identification Variable
Description

V3002
ICPSR HOUSEHOLD IDENTIFICATION NUMBER

V3003
YEAR AND QUARTER IDENTIFICATION

V3004
SAMPLE NUMBER

V3005
SCRAMBLED CONTROL NUMBER

V3006
HOUSEHOLD NUMBER

V3007
LAST TWO DIGITS OF SCRAMBLED CONTROL NO.

V3008
PANEL AND ROTATION GROUP

V3009
PERSON SEQUENCE NUMBER

V3010
PERSON LINE NUMBER


LINKAGE VARIABLES FOR RECORD TYPE 4
Identification Variable
Description

V4002
ICPSR HOUSEHOLD IDENTIFICATION NUMBER

V4003
YEAR AND QUARTER IDENTIFICATION

V4004
SAMPLE NUMBER

V4005
SCRAMBLED CONTROL NUMBER

V4006
HOUSEHOLD NUMBER

V4007
LAST TWO DIGITS OF SCRAMBLED CONTROL NO.

V4008
PANEL AND ROTATION GROUP

V4009
PERSON SEQUENCE NUMBER

V4010
PERSON LINE NUMBER


For example, to ensure that a given person record is linked to its corresponding incident record, the identification variables V3002 through V3010 on the person record could be combined and used to link with the combination of variables V4002 through V4010 found on the incident record. Variables V1001, V2001, V3001, and V4001 are one- digit record type identifiers which indicate group levels for a particular record.

Methodological Issues in the Measurement of Crime
Recall, Reference Periods, and Bounding
The NCVS uses a six month reference period. Respondents are asked to report crime experiences occurring in the last six months. Generally, respondents are able to recall more accurately an event which occurred within three months of the interview rather than one which occurred within six months; they can recall events over a six- month period more accurately than over a 12-month period. However, a shorter reference period would require more field interviews per year, increasing the data collection costs significantly. These increased costs would have to be balanced by cost reductions elsewhere (sample size is often considered). Reducing sample size however, reduces the precision of estimates of relatively rare crimes. In light of these trade-offs of cost and precision, a reference period of six months is used for the NCVS.

A common concern of researchers employing reference periods in retrospective surveys is telescoping. Telescoping refers to a respondent's misspecification of when an incident occurred in relation to the reference period. For example, telescoping occurs if a respondent is asked about victimizations within the last six months and erroneously includes a victimization that occurred eight months ago. Telescoped events which actually occurred prior to the reference period can be minimized at the time of the first interview by a technique known as bounding. Bounding is achieved by comparing incidents reported in an interview with incidents reported in a previous interview and deleting duplicate incidents that were reported in the current reference period. In the NCS and NCVS designs, each visit to a household is used to bound the next one by comparing reports in the current interview with those given six months prior. When a report appears to be a duplicate, the respondent is reminded of the earlier report and asked if the new report represents the incident previously mentioned or if it is different. The first interview at a household entering the sample is unbounded, and data collected at these interviews are not included in NCS and NCVS estimates. However, if a household in sample moves and another moves into that address, the first interview with the replacement household is unbounded but is included in NCS and NCVS estimates.

Proxy Interviews
Proxy interviews are currently conducted for: (1) household members aged 12 or 13 if a knowledgeable household member insists they not be interviewed directly by the interviewer, (2) persons incapable of responding due to physical or mental incapacity, and (3) those persons who are away from the household during the entire interview period.

Using the Online Data Analysis System
The Online Data Analysis System is a set of programs for the documentation and web-based analysis of survey data and procedures for creating customized subsets of datasets. Online Data Analysis is available for NCVS only with the concatenated incident-level file, not the full file. The unit of analysis for that file is the crime incident.

Online data analysis is recommended for users who would like to search for variables of interest in a dataset, review frequencies or summary statistics of key variables to determine what further analyses are appropriate, review frequencies or summary statistics for missing data, produce simple summary statistics for reports, create statistical tables from raw data, and those who would like to create custom subsets of cases or variables from a particularly large collection to save time in downloading and space on a personal computer.

Other NCVS Resources
Web Sites
American Society of Criminology Division on Women and Crime
http://www.asc41.com/diviwomcrim.htm

American Statistical Association Committee on Law and Justice Statistics
http://www.amstat.org/comm/index.cfm?fuseaction=commdetails&txtComm=CA02

Bureau of Justice Statistics
http://www.ojp.usdoj.gov/bjs/

Centers for Disease Control Division of Violence Prevention
http://www.cdc.gov/ncipc/dvp/dvp.htm

Crimes Against Children Research Center
http://www.unh.edu/ccrc/

Institute for Law and Justice: Domestic Violence Site
http://www.ilj.org/dv/index.htm

Institute for Law and Justice: Sexual Assault Site
http://www.ilj.org/sa/index.htm

National Center for Juvenile Justice
http://www.ncjj.org/

The National Institute of Justice's Data Resource Program
http://www.ojp.usdoj.gov/nij/dataprog.htm

Office for Victims of Crime
http://www.ojp.usdoj.gov/ovc/

Office of Justice Programs; Violence Against Women Office
http://www.ojp.usdoj.gov/vawo/

Publications
The link below will search the ICPSR citations database for citations of publications with "National Crime Victimization Survey" in the title. Users can create their own searches or browse the citations database through our Publications Bibliography Web page.

Search for NCVS Publications




Naval Health Research Center, San Diego, CA Return: Behavioral Science & Epidemiology

The Accuracy of Self-Report
Surveys of Illegal Drug Use




The Department of Defense (DoD) survey of Health Related Behaviors Among Military Personnel is a self-report survey of the substance use behaviors of U.S. military personnel (Bray et al., 2003). When researchers plan surveys like this, they realize that some people may not honestly answer sensitive questions about illegal or socially questionable behaviors such as drug use. They may feel embarrassed or threatened if they tell the truth. Perhaps people have forgotten what really happened. These factors are considered in doing surveys.

In the DoD Survey of Health Related Behaviors these problems are probably as small as they can be. There is simply no reason to lie. Everyone who participates is promised that their answers will remain anonymous and secret. The survey did not ask for names, social security numbers, or any identifying information. A civilian research company conducted the survey and it is impossible to tell what answers anyone gave or to punish anyone for honestly reporting drug use.

When surveys are done like this, even military personnel are willing to admit to drug use. However, willingness to admit drug use is severely reduced when military personnel answer a survey that they know will be part of their official records. For example, in a large survey of 11,000 Navy personnel in basic training from 1996 to 1997 (Olson, Stander, & Merrill, 2004; Stander & Merrill, 2004):

26% admitted to drug use in the year before they joined the Navy on a confidential (secret) and completely anonymous (no names collected) survey administered by civilians just like the DoD survey.

21% of Navy recruits in basic training admitted drug use in the year prior to entering the military even when the survey was confidential (secret) but they were asked for their names.

Among the exact same Navy recruits who participated in the confidential survey, less than 1% admitted they had ever had a problem with drugs on a military medical survey that was part of their personnel records.

Although there is no reason to lie when a survey is anonymous and confidential, some people still may not admit drug use. How much might this bias survey results? One way we can estimate the bias is to look at how many people seem to have been discouraged from telling the truth on the Survey of Navy Recruits when they were asked for their names. The results when the survey was completely anonymous and no names were collected were almost 25% higher (1.24 times).

Another way to estimate the amount of bias in the results of self-report surveys is to consider studies of drug use in other types of workplaces. For example, in a study to assess drug use in a civilian workplace, researchers compared self-reports of drug use against reports from urinalysis and hair analysis testing. They estimated that actual rates were 50% higher than the number of people who admitted to drug use (Cook, Bernstein, & Andrews, 1997).

We can use both of these estimates of bias in self-report survey results to estimate the impact on the 2002 DoD Survey of Health Related Behaviors. For example, the DoD survey found that only 7.9% of U.S. Marine Corps personnel had used any illegal drugs in the last 12 months. If we adjust this figure up by 25% to 50%, we still estimate that 88% to 90% of all Marines on active duty are completely drug free each year.

Bray, R. M., Hourani, L. L., Rae, K. L., Dever, J. A., Brown, J. M., Vincus, A. A., et al. (2003). 2002 Department of Defense Survey of Health Related Behaviors Among Military Personnel (Final Report RTI/7841/006-FR). Research Triangle Park: Research Triangle Institute.

Cook, R. F., Bernstein, A. D., & Andrews, C. M. (1997). Assessing Drug Use in the Workplace: A Comparison of Self-Report, Urinalysis, and Hair Analysis. In L. Harrison & A. Hughes (Eds.), The validity of self-reported drug use: Improving the accuracy of survey estimates (Research Monograph No. 167) (pp. 247-272). Rockville, MD: U.S. Department of Health & Human Services, National Institutes of Health, National Institute on Drug Abuse, Division of Epidemiology & Prevention Research.

Olson, C. B., Stander, V. A., & Merrill, L. L. (2004). The Influence of Survey Confidentiality and Construct Measurement in Estimating Rates of Childhood Victimization Among Navy Recruits. Military Psychology, 16, 53-69.

Stander, V. A., & Merrill, L. L. (2004). [Results From the Naval Health Research Center Survey of Navy Recruits]. Unpublished raw data.

Answer 2

1

Answer 3

Uniform Crime Reporting Survey

Answer 4

Nothing. They are the same thing. The NCVS is info that is gathered by the government directly from the victims through things like the census. The crime did not, and may never have, been reported to the police. The Uniform Crime Report is info that the feds compile from stats that work their way up from police departments. Obviously that info had to have been reported to the police by the victims. The NCVS tends to show much higher rates of some crimes (like petty theft) than the UCR. Victims dont report all crime to the police.