44. Dr. Megan Moreno sent a cautionary message to a randomly selected half of a sample of MySpace users (ages 18–20) whose public profiles included references to sex and substance abuse. A review of all profiles from the original sample three months later showed that those who had received the email were more likely to have removed the references from their online profiles or to have changed their profile setting to “private.” Is this an experiment or observational study, and how do you know?