Illinois uses the standardized data collection methods developed by CDC and used by all PRAMS participating states. Data is collected through mailed surveys with telephone follow-up for nonresponders. A stratified systematic sample of approximately 200 mothers is selected monthly from a frame of eligible birth certificates. At two to six months after delivery, each sampled mother is mailed an introductory letter followed by a 14-page survey. A reminder letter, second, and third mailing of the survey are sent to those who do not respond to earlier surveys. PRAMS interviewers telephone mothers who do not respond to any of the mailed surveys and administer the survey by telephone. Surveys are sent in both English and Spanish and telephone interviews are conducted in both languages.
Statistics are based on weighted data. The weights were developed by CDC to adjust for sample design, nonresponse patterns and omissions from the sampling frame. The final sampling weight used in the analysis of the survey data is the product of these three elements. Weighting is necessary to give unbiased estimates of population parameters. PRAMS data are representative of Illinois resident women, age 14 or older, who have given live birth in Illinois. The data are not applicable to all pregnant women. Women younger than the age of 18 are not asked questions about physical abuse.