NEW YORK -- It's a question that often prompts a boastful answer or a bashful one: How many sex partners have you had?

Now the federal government says it has authoritative statistics, documenting that men are far more likely to play the field than women.

A new nationwide survey, using high-tech methods to solicit candid answers on sexual activity and illegal drug use, finds that 29 percent of American men report having 15 or more female sexual partners in a lifetime, while only 9 percent of women report having sex with 15 or more men.

The median number of lifetime female sexual partners for men was seven; the median number of male partners for women was four.

The survey, released Friday, is based on data collected from 1999 to 2002 for the National Center for Health Statistics, a branch of the Centers for Disease Control and Prevention.

In previous versions of this survey, participants were asked questions in face-to-face interviews. The CDC believes that caused underreporting of behaviors which might be viewed negatively, although the new survey did not provide any comparative results from earlier reports.

This time, data was gathered from 6,237 adults, aged 20 to 59, in what are called computer-assisted self-interviews -- a method designed to provide complete privacy and produce more honest answers.

"This is the first time we've used this technique," said Dr. Kathryn Porter, who served as medical officer for the survey. "The participants have a headset on, they hear questions, they touch the screen with responses. There's no one else in the room, and they can take as long as they want."

Though the survey results were presented by the CDC without subjective comment, they will likely provide ammunition to various parties in the ongoing national debate over sex education and access to birth control.

Many of the conservative groups aligned with the Bush administration on social issues promote the goal of sexual abstinence until marriage. The survey found only about 11 percent of never-married adults had remained chaste.

Among the other findings:

• About 96 percent of U.S. adults have had sex.
• Sixteen percent of adults first had sex before age 15, while 15 percent abstained from sex until at least age 21.
• Twenty-five percent of women and 17 percent of men reporting having no more than one partner of the other sex in their lifetime.
• Twenty-six percent of men and 17 percent of women have tried cocaine or other street drugs (not including marijuana) at some time in their life. Seven percent of men and 4 percent of women had done so within the past 12 months.

The survey, formally titled the National Health and Nutrition Examination Survey, did not include the homeless, prisons inmates or other institutionalized adults.