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Nat Geo Statistics with Audio

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Nancy Pfenning

on 6 June 2013

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Transcript of Nat Geo Statistics with Audio

Statistics to Better Know and Nurture Our World Statistical analysis of snow leopard behavior helped this environmentalist develop an insurance plan for herdsmen that protects predator and prey. Study design: Conservationists used interviews with herdsmen, and clues like scat and footprints, to estimate how many snow leopards live in Pakistan's mountains: 300 to 420. Relative to each of the 3 species, the z-scores are
(9.7-11.49)/0.79 = -2.27 compared to P. boisei
(9.7-7.80)/0.68 = +2.79 compared to H. erectus
(9.7-9.27)/0.57 = +0.75 compared to early Homo
These z-scores, plus study of other facial bones, led the Leakeys to announce a new branch of the early Homo family that lived in East Africa 2 million years ago. Sampling design: Conservationists randomly selected transects throughout South Sudan and counted the number of antelope in each. Summarizing categorical variables: 437 of New York City's 592,130 trees experience a "conflict" with sneakers; 35% are affected by overhead wires. A single quantitative variable---tooth size---can guide paleontologists to identify a species of early man based on a small fragment. The key is to calculate z-scores: Lengths in millimeters of the back molar tooth "P4" have...
Paranthropus boisei: mean 11.49, s.d. 0.79
Early homo erectus: mean 7.8 , s.d. 0.68
Early homo (not erectus): mean 9.27, s.d. 0.57
In 2012, the Leakeys discovered a 9.7-mm P4 tooth in Kenya. Could it easily belong to any of these three species of early man? Based on the samples, over a million antelope are estimated to roam the country: good reason to caution the government not to develop too much of the land for oil drilling. Why does the colorful puffleg hummingbird risk extinction... This hummingbird is highly specialized in terms of habitat (only a certain part of Colombia's Andes Mountains) and diet (nectar from certain types of flowers). ...while the common crow thrives in great numbers? The crow can live practically anywhere in the world, and eats all sorts of food, from grains to carrion. Ornithologists regressed extinction risk on degree of specialization (in terms of habitat, diet, etc.) for all species of bird, resulting in a correlation of r= +0.92. Thus, conservationists have learned to concentrate their efforts on protecting species that are highly specialized. Thus, the laws of probability teach us about all sorts of aspects of our world, from history to heredity. Researchers found that 8% of men in Asia share a particular variation on the Y chromosome. Their most recent common ancestor must have lived in Mongolia about 34 generations ago. According to the Multiplication Rule, the probability of randomly passing along that chromosome to one offspring and the next and the next and the next..., through more than 30 generations, is less than 0.0000000001. Researchers connected this improbably high level of genetic material with Genghis Khan's sweeping conquest of Asia close to 1,000 years ago. The practice of fathering large numbers of offspring by harems and concubines helped him and his son and grandson "stack the deck" in favor of their own genes. Little is known about the Mayans' rites of human sacrifice. Were their victims for the most part adolescent females? Archaeologists recently studied 15th-century records of the Spanish Inquisition; interrogations by Bishop Calderon produced accounts of where the Mayans held rituals in highly inaccessible underwater caves, called cenotes. Based on the mean and s.d. of n skulls sampled at random from this population, the z-score for sample mean diameter was so large that archaeologists are convinced the victims were mostly adolescent males. Environmentalists helped residents of Benin, West Africa, install solar irrigation for their crops. In a background survey of energy sources, 0.28 of 365 respondents said they lit their homes with "Yayi Boni." Further inquiry revealed that Yayi Boni is an ingenious low-energy device--affectionately named after their president--created from LEDs glued to a CD to reflect, and lit by batteries. Methods of statistics show that the proportion of all residents lighting their homes with Yayi Boni is 28% plus or minus 5%: Between 23% and 33% of the district's population use this device which is virtually unknown in our part of the world. Those records led divers to caves containing bones of dozens of victims. We know that adolescent Mayan female skull diameters varied with a certain mean and standard deviation. Ecologists use statistical methods to estimate the biomass of various species that compete for resources in a given region---such as grasshoppers in Kenya's Turkana Basin. 496 grasshopper weights had mean 0.446 g and s.d. 0.161 g. A 95% confidence interval for population mean weight is (0.432, 0.460). After estimating counts of grasshoppers per area of a given size, total biomass is estimated at 272 to 290 kg (more than 600 lbs) per squared km. Turkana goats' estimated biomass is 260 lbs per sq km: less than half that of the grasshoppers. As a follow-up, it was found that grasshoppers' biomass was less in a nearby area that excluded goats, suggesting a symbiotic relationship between the two species. Europe is full of ancient man-made structures, from Roman roads to cliffside castles. How can historians estimate their ages? When a quarried stone is exposed to light and air, it can become the birthplace of lichen. Sizes were found to increase linearly with ages known from historical records, at a rate of about 1 inch every 750 years. Alpine archaeologists can predict a structure's age based on the size (in cm) of the largest lichen patch on its stones: Age = 70 + 175(Size) Sharing is an almost exclusively human behavior, but some chimpanzees are known to share meat with others. Recently, chimps in Senegal were observed sharing not just food but also tools. "Owners" were almost always males; "recipients" were sometimes males, sometimes females. 28 females: 18 recipients of food, 10 of tools; 13 males: 13 recipients of food, 0 of tools. A chi-square test results in a P-value of 0.01: Female chimps are significantly more likely than males to receive tools, as opposed to food. A fascinating aspect of the behavior of living creatures is how they act in groups, from swarms of locusts to schools of fish, to... Crowds of people: Researchers at Oxford planted various sized groups of individuals to gaze at the top of a nearby building. ANOVA was used to demonstrate that group size played an important role: Pedestrians were significantly more likely to follow the gaze of many, as opposed to few. Wildlife Biologist Malik Doka Environmentalist/Anthropologist Shafqat Hussain Data Scientist Jake Porway Paleontologists Meave and Louise Leakey Ornithologist Cagan Sekerçioglu Geneticist Spencer Wells Underwater Archaeologist Guillermo De Anda Environmental Scientist Jennifer Burney Entomologist Dino Martins Alpine Archaeologist Patrick Hunt Biological Anthropologist Jill Pruetz Behavioral Ecologist Iain Couzin This virtual journey around the world demonstrates what statistical methods can reveal to us about the big picture of our Earth: all the people, creatures, and variables that make it such a fascinating place.
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