Elizabeth L. Jeglic, a clinical psychologist who studies sexual violence prevention at John Jay College in New York, said she could not comment specifically on the CDC methodology, but she said sampling and response rate can affect findings. “If the question is asked about lifetime occurrence and younger girls are not being sampled (or less likely to be sampled) you will likely see a higher prevalence rate as older girls will have more years to experience sexual violence than younger girls,” she said in an email.