Sex education may be taught informally, such as when someone receives information from a conversation with a parent, friend, religious leader, or through the media. It may also be delivered through sex self-help authors, magazine advice columnists, sex columnists, or sex education web sites. Training can also be provided through multimedia resources. Adolescents spend a lot of their time on social media, or watching television. Those same adolescents may also have a hard time talking to their families about sexual matters. A study has shown that mass media interventions; for example, use of teaching sexual education through commercials shown on television, or ads on social media, have proven effective and decreased the amount of unprotected sex. Formal sex education occurs when schools or health care providers offer sex education. Slyer stated that sex education teaches the young person what he or she should know for his or her personal conduct and relationship with others. Gruenberg also stated that sex education is necessary to prepare the young for the task ahead. According to him, officials generally agree that some kind of planned sex education is necessary.