Let's talk about sex.
Nearly 6,000 people between the age of 14 and 94 did so at the behest of Indiana University researchers, who this week published results from their national survey. These respondents said, among other things, how often they have sex with people of the same or opposite genders; which sexual practices they engage in; and whether they used condoms. Sex researchers say it is the first study of this scope and scientific rigor since 1992, when the University of Chicago's National Opinion Research Center surveyed nearly 3,500 people.
The survey's results are fascinating, but not the final word on sex in America. While researchers took care to find a representative sample of people, the survey population limits or omits a few key groups that could have skewed the results, some health researchers say. And because of the inevitable challenge studies on sex face in persuading people to respond honestly, the findings should be treated with some skepticism.One area of inquiry that tends to draw a lot of interest can be especially problematic, statistically speaking: comparing how each gender reports on sex. That came into play in the latest study, which found that boys age 14 to 17 say they use condoms 79% of the time during intercourse, compared to just 58% of girls in that age group who said their male partners used condoms.
Numbers Guy Blog
Those numbers might suggest that boys are exaggerating their condom use, or that girls are underreporting it. But the potential mismatch between the sexual encounters each group described also might account for some of the difference. Some respondents might have been having sex with people outside the 14-17 age range. This could affect the results if age influences whether someone uses a condom.
"Sometimes people portray this as if men and women in surveys are closed populations," says William Mosher, a statistician at the Centers for Disease Control and Prevention's National Center for Health Statistics, about the comparisons between male and female sexual behavior. "They are not closed populations."
Then there is the challenge of ensuring that people answer honestly about deeply private matters. Researchers who led the Indiana study acknowledge the difficulty of obtaining truthful information. "There is no perfect method," says Debby Herbenick, research scientist at Indiana University and co-author of the study.
Nonetheless, she says the Indiana group's approach had certain advantages. Researchers hired the survey company Knowledge Networks to interview people electronically. Many pollsters are skeptical of Web surveys because not everyone in the U.S. is online—or online often enough to see ads for Internet-based panels. But Knowledge Networks takes a different approach, contacting people via mail by randomly selecting addresses, and persuading about one in four or five to join a panel. If panelists lack the means to answer online polls, the company equips them.
Another problem with the study: Soldiers, prostitutes and Americans living abroad are unlikely to participate in sex surveys, either because they are outside the geographical range, or because they are reluctant to talk about illicit activities. Their absence can affect results, researchers say.
The survey also had limited statistical power to describe the sexual habits of subgroups of Americans, because of small sample sizes. This prevented researchers from learning much about same-gender sex. And, for instance, an analysis of whether black women who used marijuana before sex also used condoms was hampered by the presence of just eight such women in the sample.
While the anonymity of online surveys might make respondents more comfortable responding honestly, it also can be harder to verify their identity—perhaps the person who claims to be a 45-year-old woman is actually a 20-year-old man. For the last comprehensive survey on Americans' sexual behavior in 1992, researchers faced a different set of issues. Online polling wasn't an option, so interviewers went to people's homes, explains Robert T. Michael, an economist at the University of Chicago and a principal investigator on the study. To persuade respondents to divulge highly personal information, pollsters appealed to people's desire to help supply information and fight the spread of AIDS. "We had a compelling rationale, and our field people were good," Prof. Michael says.
"It's exciting, intellectually challenging research," Prof. Michael says of sex studies. "It's important to get it right."
Copyright 2009 Dow Jones & Company, Inc. All Rights Reserved
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Sex, and Studying It, Are Complicated
My print column this week examines the fascinating numbers and tricky statistical issues that accompany sex surveys, such as a high-profile one published by Indiana University researchers this week.
This study in many ways is a descendant of one conducted by the University of Chicago’s National Opinion Research Center in 1992. Such studies are so infrequent because sexual research that looks beyond fertility and sexual health issues can be hard to fund, researchers say.
The latest study emerges in a different research climate than the one that produced the 1992 study. The Indiana study makes use of online polling, which wasn’t an option last time around. Knowledge Networks, which conducted the survey, uses mailing addresses to recruit its panel and provides Internet access to households that need it. This helps overcome some potential methodological drawbacks to online research, which also has an important potential advantage for research asking about sensitive topics: It allows researchers to ask about sex without ever personally asking anyone about sex. On the phone or in person, there is “more risk that respondents and research subjects are going to be less honest in their responses,” because of their desire to please interviewers, or not be embarrassed with them, said J. Michael Dennis, executive vice president at Knowledge Networks.
Another important advantage for online polling is cost. “For face-to-face interviews, to get really large numbers, it is considerably expensive,” said Debby Herbenick, research scientist at Indiana University and co-author of the recent study.
Then there are all the inherent challenges with getting people to talk about sex, for which pollsters have devised a wide range of strategies. For the 1992 survey, interviewers avoided asking directly about sensitive topics, either by giving respondents some questions in writing or by using a clever way to cloak their responses. When asking about which kinds of sexual behavior was involved in respondents’ most recent sexual encounter, interviewers would hand over a card where letters corresponded to various options, such as oral sex, and respondents would tick off letters. Interviewers didn’t have the key to the card.
In addition to the interview mode, other characteristics differ between the two surveys — notably questions asked. That lessens the ability to track trends between the surveys.
Funding also differed. The older study was planned with the promise of Congressional money, but when North Carolina Republican Jesse Helms led an effort to block in the Senate, researchers had to delay and turn to other sources, including foundations. The newer study bypassed governmental sources, receiving funding for data collection from Church & Dwight Co., the makers of Trojan condoms. Condoms are a major topic in the research. Herbenick said the company didn’t dictate study design, though it did offer advice.
These surveys nonetheless are broader and in some ways more reliable than the federal government’s efforts to track sexual behavior, which generally are part of broader studies. The Centers for Disease Control and Prevention’s Youth Risk Behavior Surveillance System, administered in schools, asks just seven questions about sex. It also doesn’t define sex, out of fear that more schools or parents would opt their students out of responding. “We want to ask appropriate questions, but at the same time, we don’t want to create any unnecessary red flags,” said Laura Kann, who helps direct the survey.
Meanwhile, the National Survey of Family Growth, run by the CDC’s National Center for Health Statistics, focuses on reproduction, so it covers only ages 18 to 44, and only in 2002 did it begin to survey men in addition to women.
One finding many of these surveys share is that the stories men and women tell about their sex lives don’t always match up as we’d expect. Typically, men report more sex partners than women do. Also, in the latest survey and in recent studies of college students, more men report their partners achieve orgasm in their latest sexual encounters than the proportion of women who report achieving orgasm, a finding which has received extensive press coverage.
Researchers who have found these results attribute them generally to poor communication between men and women in bed. “We all need to do a better job of communicating,” Herbenick said.
But such findings may be problematic when certain groups are excluded. Robert T. Michael, an economist at the University of Chicago and a principal investigator on the study, pointed out that prostitutes are unlikely to tell strangers about their sex habits, and those with many clients may have a major effect on estimates of average number of sex partners.
His collaborator on the 1992 study, Edward Laumann, said that because of such discrepancies, “people could be describing the same thing,” yet their answers still could add up to different numbers for each gender.
William Mosher, a statistician at the National Center for Health Statistics, added that these surveys generally are fixed on a certain age range, and don’t ask people outside the country about their sex habits — both factors that could lead to mismatches between male and female responses.
This doesn’t necessarily mean that the orgasm reporting gap isn’t real, or even bigger than found — just that there are potential confounding factors. Stanford University sociologist Paula England, who has collaborated on the college studies, said these findings hold up among various subcategories of respondents — which suggests that at least in this population, if not necessarily in the overall population, sex isn’t always perceived the same way by both partners. And Pepper Schwartz, a sociologist at the University of Washington, said a study she worked on in the 1980s found a similar effect, though not as large, among couples — who presumably were reporting on the same sexual encounter. “The direction or percentage might have some wiggle room, but the message is pretty clear,” Schwartz said.
Copyright 2008 Dow Jones & Company, Inc. All Rights Reserved
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