HIV and men who have sex with men sexual activity with members of the same sex, regardless of how they personally identify themselves. Many MSM choose not to (or cannot for other reasons) identify as homosexual or bisexual. Similarly, the label excludes men who identify as gay or bisexual, but who have never had sex with another man, including many gay teenagers. The terms MSM and women who have sex with women (WSW) have been used in medical scholarship since at least 1990. But, the term has been attributed to Glick "et al.", because their usage in a 1994 study solidified the concept in medical terminology. MSM is
Moving average "S" to "Y" as shown above, though other techniques exist, such as setting "S" to an average of the first 4 or 5 observations. The importance of the "S" initialisations effect on the resultant moving average depends on "α"; smaller "α" values make the choice of "S" relatively more important than larger "α" values, since a higher "α" discounts older observations faster. Whatever is done for "S" it assumes something about values prior to the available data and is necessarily in error. In view of this, the early results should be regarded as unreliable until the iterations have had time