Supp Statement NIS-B

B. Collection of Information Employing Statistical Methods

1. Universe and Respondents Selection

1.1. State Prisons

The frame for sample selection is provided by the 2005 Census of State and Federal Correctional Facilities. The Census includes aggregate-level data on the number and characteristics of inmates housed, as well as data on the facility age and type (confinement or community-based), security level, court orders, facility programs and policies, health and safety conditions, confinement space, employment, and operating costs. In cases where the 2005 Census is not available, data from individual facilities and/or the 2000 Census will be used. The universe for the NIS will include all confinement facilities in the Census which includes 1,214 facilities and 1.2 million inmates.

There will be a two stage sample selection process that will allow for both national and facility level estimates. The first stage will select a nationally representative sample of 140 state prison facilities. The first stage sample will be selected with probabilities proportionate to the inmate population while ensuring that at least one facility is selected in each state. Furthermore, the size measure for the female population will be increased so that the expected number of female inmates selected is doubled in order to allow for meaningful analysis by gender. Facility selection will be conducted using Chromy’s PPS algorithm (Chromy, 1979) with the frame sorted by region, state, and gender of facility. This will ensure that, in expectation, the number of facilities selected in each region and state will be proportionate to their size measure (female facilities will be oversampled). In the second stage a simple random sample of inmates will be selected from a roster of inmates generated immediately prior to data collection. The expected, average prevalence rate within state prisons is 4.0%. Based on this expectation, the within facility sample size is designed to produce a standard error of 0.015 in order to minimize the number of facilities whose confidence interval includes zero. Moreover, due to the varying sizes of state prisons, a finite population correction factor will be applied to the sample size to minimize burden on smaller facilities. Also, the facility-level sample design assumes a 75% response rate and sampled inmates will be randomized such that they have a 10% chance of not receiving the sexual assault questionnaire.

1.2. Federal Prisons

The frame for Federal prisons will be based on the 2005 Census of State and Federal Correctional Facilities which includes 84 Federal prisons. There will be a two stage sample selection process that will allow for national and facility level estimates. In the first stage, a nationally representative sample of 10 facilities will be selected with probability proportionate to the size of the inmate population. In order to allow for meaningful analyses by gender, the size measure for female facilities will be increased in order to double the expected number of female inmates selected. The second stage of sample selection will be conducted in the same manner as described for state prisons.

1.3 Jails

The frame for local jails will be based on the 2005 Census of local jails. The NIS will consist of both public and private local jails identified on the 2005 Census which includes 3,365 jails. There will be a two stage sampling process that will allow for nationally representative and facility level estimates. The first stage will select jail facilities with probability proportionate to the inmate population in the facility. The first stage will be designed such that 300 jails are selected. In the second stage a simple random sample of inmates will be selected from a roster of inmates generated immediately prior to data collection. The expected prevalence rate within a particular jail is 2.0%. Based on this expectation, the within facility sample size is designed to produce a standard error of 0.01 in order to minimize the number of facilities whose confidence interval includes zero. Moreover, due to the varying sizes of local jails, a finite population correction factor will be applied to the sample size to minimize burden on smaller facilities. Also, the facility-level sample design assumes a 70% response rate and sampled inmates will be randomized such that they have a 10% chance of not receiving the sexual assault questionnaire.

The table below illustrates the size of the NIS universe by facility type.

Facility type	Number of facilities
Total	5,033
Prisons
Public - Federal	84
Public – State	1,320
Private	264
Local Jails
Public	3,318
Private	47

2. Procedures for Information Collection

Data collection procedures include computerized interviewer-administered interviews, Audio Computer-Assisted Self-Interviews, and paper and pencil surveys.

The methods proposed for use in data collection are as follows:

1. Facility Recruitment

A sample of 450 jails and prisons will be selected from a frame of federal, state, and local correctional facilities. Each sampled facility will be contacted to solicit participation. A contact person will be designated at each facility.

b. Sampling of Inmates

Within one week prior to data collection at a facility, the facility will provide a roster of all inmates 18 and older who are currently incarcerated there. A random sample of inmates will be drawn from the roster.

c. Data Collection

A team of interviewers will visit the facility. They will ask correctional officers to bring each sampled inmate to a private interviewing area. The interviewer will read a consent form to the sampled inmate and solicit his/her participation. If the inmate consents, the interviewer will begin administering a brief set of demographic questions that includes age, race, ethnicity, length of incarceration, and reason for incarceration. After completing the demographic section, the interviewer will give the inmate a brief tutorial on answering questions on the touch screen computer and allow the inmate to answer the more sensitive questions in complete privacy. In order to allow inmates with reading difficulties to participate, the inmate will wear a set of headphones and hear the questions being read as they appear on the screen. The inmate will enter his response by touching a button on the screen – no computer expertise is required. The computer program will randomly pick a series of questions to administer. Most inmates will get the series of questions about sexual assault. However, a portion of inmates will get a series of questions about alcohol and drugs instead. No one but the inmate will know which series of questions he was asked. At the end of the inmate section of the questionnaire, he will turn the computer back to the interview and return to his housing unit. The interviewer will then finish the process by answering a set of debriefing questions about the interview.

In order to determine if there is any bias introduced from nonrespondents, administrative record data will be collected for all sampled inmates. This will allow researchers to compare demographic characteristics of responding inmates with those who did not participate.

3. Methods to Maximize Response

Every effort is being made to make the survey materials clear and simple to use. The NIS questionnaire has been designed to maximize respondent comprehension and participation and minimize burden. Some examples include an easy to use touch-screen interface with the questions simultaneously delivered via headphones. A Spanish version of the questionnaire will be available for non-English, Spanish speaking respondents. Field staff from the contractor will be available to answer any questions that respondents may have, including bilingual staff who can answer questions in Spanish. Arrangements with mental health staff at each facility, or if needed an on-call or some other arrangement, will be made for delivery of counseling services for respondents interested in obtaining counseling services or assistance following the survey.

4. Test of Procedures or Methods

The interview and data collection procedures were tested in a pilot study conducted Jan. – May 2006.

5. Consultation Information

The Corrections Statistics Unit at BJS takes responsibility for the overall design and management of the activities described in this submission, including sampling procedures, development of the questionnaires, and the analysis of the data. BJS contacts include:

Paige M. Harrison, Statistician

Corrections Statistics Unit

Bureau of Justice Statistics

810 Seventh St., N.W.

Washington, DC 20531

(202) 305-0809

Allen J. Beck, Ph.D

Principal Deputy Director

Bureau of Justice Statistics

810 Seventh St., N.W.

Washington, DC 20531

(202) 616-3277

The Principal Investigator is:

Rachel A. Caspar

Senior Survey Methodologist

RTI International

Survey Research Division

3040 Cornwallis Road

Research Triangle Park, NC 27709-2194

(919) 541-6376