Commenter Mikey Blayze writes:

The movie Precious is a perfect visual representation of the black underclass

Precious is an unbelievably heartbreaking film about a person named Precious who has every disadvantage one can have in America: She’s black, female, incredibly dark skinned, incredibly overweight, illiterate, dirt poor, physically abused, sexually abused, pregnant with her second baby, fathered by her father; The first baby has Down’s Syndrome!  And that’s just the first 20 minutes of the movie!

But other than that, Precious is not so different from other teenaged girls.  She has a crush on her math teacher, she dreams of having a light skinned boyfriend with nice hair, but first she wants to be in one of those BET videos.

So what is her IQ?

At the start of the film we are told she is 16 years old and reads at a grade 2.8 level.  Since people typically read several grades below their completed grade level,  the average kid probably wouldn’t read at grade 2.8 level until grade 5.8 (about age 10.8), so at age 16, Precious had a reading age of 10.8 implying an IQ of 68 on the old age ratio scale 10.8/16 = 0.68.

This makes sense because according to scholar Richard Lynn, the average IQ of the darkest skinned African Americans like Precious is 80 (white norms), but because Precious is also extremely overweight, and weight/height ratio is negatively correlated with IQ at about -0.22, Precious would be expected to be below this level.  Indeed I estimate Precious to be 2.5 standard deviations above the mean of her age in weight/height ratio, so we might very crudely estimate her IQ to be 2.5 SD (-0.22) = -0.55 SD (roughly -8 IQ points) from what one might expect based on race and color alone. This reduces her IQ to 72 which is very similar to the 68 IQ as measured by her reading level.  Both numbers round to 70.

It seems simple regression works, even on fictional characters created by writers who know nothing about psychometrics or statistics, and probably don’t even believe in IQ!

However watching the film, one gets the sense from her subtle sense of humour that Precious is smart despite her illiteracy, which is almost understandable given the abysmal quality of the inner-city schools she attends.

In an especially adorable scene, Precious complains about being an “insect victim”, only to have a white student tell her that insects are bugs; what Precious meant to say was “incest victim.”

“What are you a scientist now?” says Precious sarcastically.

Once Precious leaves these ghetto schools and attends an alternative high school (which I also attended as a teenager; I’m now in my thirties) we see her reading level blossoms to a grade 7.8 level in about a year, thanks to the support of a loving teacher.  The national average for American adults is 8th grade level, so this implies Precious now has an IQ around 100!

Although this film is fictional, cases like this are not that uncommon.  For example boxer Mike Tyson was considered borderline mentally retarded because of his low reading level, but under the tutoring of his boxing coach, his reading improved by about three grade levels in three months.  Such anecdotes underscore the pitfalls of using academic SAT type measures to estimate IQs.