Survey Administration

    A point of contact at each law enforcement agency in the NDTS sample is verified by NDIC personnel to ensure the survey is directed to persons familiar with the drug trafficking situation in the agency’s area of responsibility.  Typically, agencies in the sample are mailed two solicitation letters.   The first letter provides login information and requests that sample agencies use the secure NDTS web site to respond electronically.  One month later, a second letter is sent to non-respondents giving them the option to respond either electronically or complete an enclosed paper copy of the survey and return it NDIC via a prepaid postage envelope that is provided.  Responses from paper copy surveys are entered into the NDTS database designed and developed by NDIC.

Estimation Techniques

All agencies in the sample are weighted to sum to the population of the sampling frame.  Weights are adjusted for non-response and for the addition and/or deletion of agencies from the sample.  The final weight for each respondent is used to derive national-, regional-, and state-level estimates for all survey items.  The final adjusted score was summed for each response category (for example, high, moderate, and low) for each item, and the proportion of the final scores provide the national-, regional-, or state-level estimate for that item.  Some respondents did not answer all survey items.  Item non-response rates are reviewed to ensure that responses survey items are not impacted by an excessive non-response rate and NDTS data collection procedures are assessed to ensure that systemic non-sampling error is not being introduced into the data.