Selection Bias

Selection Bias occurs when a sample is not random in some way that has important consequences for the inference you want to draw from your sample. Marginal Revolution points to another study which tries to identify which types of people self select out of experiments.

Students were significantly less likely to participate if peers nominated them as being higher on narcissism or non-assertiveness. Results suggest it may be more difficult to obtain sufficient numbers of people high in narcissistic traits than individuals with other personality traits.

And who is more likely to participate?

There was a significantly higher probability of participation if peers nominated someone as having more histrionic, obsessive–compulsive,self-sacrificing, and intrusive/needy characteristics.

Keywords: Selection Bias, ECO307

Incentives and Oral Sex

While Marginal Revolution won't talk about Oral Sex, this blog will. Tim Harford has a great short piece in Slate on the much talked about increase in teenage oral sex. From the article:

The rest is basic economics. When the price of Coca-Cola rises, rational cola-lovers drink more Pepsi. When the price of penetrative sex rises, rational teenagers seek substitutes. Perhaps we shouldn't be surprised that even as the oral-sex epidemic rages, the Centers for Disease Control and Prevention reports that the percentage of teenage virgins has risen by more than 15 percent since the beginning of the 1990s. Those who are still having sex have switched to using birth-control methods that will also protect them from sexually transmitted infections. Use of the contraceptive pill is down by nearly a fifth, but use of condoms is up by more than a third. The oral-sex epidemic is a rational response to a rise in the price of the alternative.

Do you think this will raise the interest of an 18 year old undergrad in a principles class? Probably, too bad I can't send the link to my colleagues as a few of them are so uptight they might file a sexual harassment grievance against me. Its a shame really.

Keywords: Sex

Funeral Strippers

By way of Marginal Revolution and a few others, it appears that China is cracking down on the hiring of funeral strippers. Yeah, you heard me, strippers at funerals. Seems the Chinese think the more people you have at your funeral the luckier the family will be. And one way to get more people at the funeral is to hire strippers to attract aa crowd and keep them entertained.

Keyword: strippers

Update: Preventing linkrot:

Exotic dancers banned from performing at funerals in China
By Clifford Coonan and Asian Sex Gazette staffAugust 26, 2006
A striptease show is not what most mourners would expect at a funeral. But the more people that come to a funeral in China, the better the deceased is likely to fare in the afterlife, which is why some families have taken to hiring exotic dancers to keep attendance figures high.Now Chinese officials are cracking down after the state broadcaster, CCTV, ran a report about two groups of strippers performing at a farmer's funeral in the eastern province of Jiangsu. The next day, police
arrested the organisers and five women for "obscene performances". Local
officials were told they must submit plans for funerals within 12 hours after a
villager dies. Exotic dancing is off the menu - and residents can report
"funeral misdeeds" on a special hotline for a reward of USD $ 35.

In China mourners wear white, not black, and funeral processions are led by men clashing cymbals and playing musical instruments. Other mourners set off firecrackers. The local people believe that the more people gathered at a funeral, the more luck it will bring to the family and offspring. So some families hire striptease troupes to attract more people, the report said. This stripping spectacle has reportedly had become one of the town's most popular nighttime events, especially among migrant workers. Some local residents even hosted a rival shows with two performances on the each side of the street close to the mourning hall and their houses to attract viewers. With a competitive atmosphere, the dancers and singers on each side try their best to attract people's attention, the report said. Some strippers even take off the trousers of male viewers and persuade them to join in the dancing, while others bathe in public or perform nude with snakes. Dozens of troupes operated stripteases in the small town, which reportedly brings in a great fortune. A troupe boss told a CCTV reporter that he earned more than 200,000 yuan (US$25,000) last year, while a male singer in the troupe said he had purchased three apartments, one in town, one in Lianyungang, a port city of Jiangsu Province, and a small one in Nanjing, Jiangsu's capital. Most of the dancers are local women, who perform for an income of 200 yuan per show, the boss said. For USD $180, dancers will stand on top of a van singing and dancing. Once the van gets to the cemetery, the women strip off. Two years ago, a family in the southern province of Fujian paid a dance troupe US $150 to take part in a funeral service for their 70-year-old grandmother. Five women danced around in their underwear and attracted an audience of about 20.

Grade Inflation

Brad DeLong confesses to grade inflation in his 101b class. Seems he thinks the students should do no worse than they would have done in the go slower do less 100b. I guess we need to consider giving all A's to anyone in economics, because it is infinitely harder than anything in marketing.

We are keenly aware that almost everybody signing up for this course could alternatively take and do very well in Economics 100b. We are anxious not to have students vote with their feet for an easier course and learn less because they fear the consequences of lowering their grade point average. Therefore this course will have a high curve: the idea is that nobody should get a lower grade than they would have gotten had they decided to take Economics 100b.

Keywords: Grades

Porn and Prostitution

Here is an excellent discussion of the precarious distinction between being a porner and a panderer. Issues that will soon be decided in FL in the Ray Guhn case.

Morality and Law

According to this article (nsfw):

Following are overall results for the single question asked in the survey — “Do you consider it to be morally acceptable to view pornographic websites and videos?”:

Yes — 21 percent No — 73 percent Not Sure — 4 percent Refuse to answer — 2 percent

According to the poll, women more frequently had a negative opinion of adult entertainment, with 81 percent of those surveyed saying they found it morally objectionable. On the other hand, 44 percent of men ages 18 to 34 said they have no objection to adult websites.

Morality in Media wasted no time issuing a press release claiming the poll proves a majority of Americans would like to see an end to adult entertainment, and other conservative groups and media outlets, such as Concerned Women for America and CitizenLink, issued similar press releases and editorials.

But it does not follow that people want to see an end to adult entertainment. There are many people who do not believe the law should dictate morality, even some of those who answered the survey. For example many people feel divorce is morally wrong, though they would not want to see a law against it. Looking at the GSS (statistically much better than any Harris Poll) we see that generally only about 40% of people feel there should be laws against the distribution of pornography whatever the age. And the trend has been ever so slightly downward

Which of these statements comes closest to your feelings about pornography laws?
	1973-2004	1973-1989	1990-2004
There should be laws against the distribution of pornography whatever the age	40.1	41.5	38.4
There should be laws against the distribution of pornography to persons under 18	54.7	52.2	57.8
There should be no laws forbidding the distribution of pornography	5.2	6.3	3.8

Morality in the Media carefully avoid actually calling for new laws rather they actually point out that the current obscenity standard appeals to the local community mores, which they argue the Harris poll clearly establishes.

Keywords: Porn, Surveys, BUS230, ECO307

A Great Line

Here is a great line from a recent post by Arnold Kling:

...and I continue to say that as a conservative/libertarian I would rather have a Democratic President who listens to Democratic economists than a Republican President who does not listen to Republican ones.

Amen.