Because the CPFFCL data collection was a census with no sampling, each crime lab was initially self-representing and had a design weight of 1. BJS developed weighting class adjustments for the 2002, 2005, 2009, and 2014 CPFFCL data to compensate for unit nonresponse and reduce nonresponse bias.
Sixteen subpopulations of labs were stratified into groups by crossing four categories of jurisdiction (federal, state, county, and municipal) and four categories of staff size (9 or fewer, 10 to 24, 25 to 49, and 50 or more). A seventeenth stratum was assigned to the FBI crime laboratory, given its unique size of more than 500 employees. Within each of the subgroups, statistical weights were applied to the data from the crime labs that responded to the census to allow their responses to represent the labs that did not respond.
Publicly funded federal, state, and local forensic crime
laboratories currently operating in United States.
Of the 409 eligible crime labs that received the questionnaire, 360 (88%) provided responses to at least some of the items. Of the 360 respondents, 351 (98%) completed the questionnaire through the automated web system.