5 out of 100 Jakarta students have had pre-marital sex

A recent research by a Ph.D. candidate at the University of Indonesia's Public Health Department discovered that five out of one hundred high school students in Jakarta have had sex.

The research surveyed 8941 students from 119 high schools, or equivalent, in Jakarta. It grouped sexual behaviors into eleven categories: sex (I assume sexual intercourse), oral sex, petting, and eight other categories which include chatting and hugging. The survey results for the most interesting categories are as follows -- behavior (% female / % male / % total): sexual intercourse (1.8 / 4.3 / 3.2), oral sex (1.8 / 4.5 / 3.3), petting (2.2 / 6.5 / 4.5)

Here's what I found interesting; please help me understand the statistics.

First, what it means by sex is not clear. (What's not clear about sex, c'mon!) Where does the 5 out of 100 figure come from? My best bet is only when sex here is defined as both sexual intercourse as well as oral sex.

Since 3.2% of the respondents does sexual intercourse, thus there is 1.8% who does only oral sex. This means 1.5% of those doing oral sex also does sexual intercourse. So far so good. But then it also indicates that there is 1.7% respondents who does sexual intercourse (more than 50% of them) without having oral sex. This can mean three things: the definition is not correct, my argument is flawed, or these kids are having a boring life!

Second, the proportion of male-female. Taking a big assumption that the respondents are split evenly 50-50 between males and females, I can argue from the study, referring to the population surveyed, that there are more "active" male students than their female counterparts.

However, it could be that: (1) the female students who have sex are doing so with more than one male student partners, or (2) the male students have sex with not only female students (perhaps with "tante"), or (3) there have been survey errors, from both males and females (e.g. courtesy bias, prestige seeking, social desirability response bias)

The newspaper/reporter should've done a better job explaining this. But I think in Indonesia we still lack individuals with good knowledge in statistics and/or market research. Reporters or politicians can easily swing a survey to the direction they want -- intentionally or unintentionally.

Nevertheless, a good research. We probably are more interested in knowing what the 119 schools are...