Questions and Answers of The Analysis Of Biological Data

A four-year review at the Provincial Hospital in Alotau, Papua New Guinea (Barss 1984), found that about 1/40 of their hospital admissions were injuries due to falling coconuts. If coconuts weigh on
Can a human swim faster in water or in syrup? It is unknown whether the increase in the friction of the body moving through the syrup (slowing the swimmer down) is compensated by the increased power
Astronauts increased in height by an average of approximately 40 mm (about an inch and a half) during the Apollo–Soyuz missions, due to the absence of gravity compressing their spines during their
The population of the giraffe-necked weevil, pictured here, is distributed over hundreds of rainforest patches of eastern Madagascar. To estimate mean neck length of males (which is much longer than
Two different researchers measured the weight of two separate samples of ruby-throated hummingbirds from the same population. Each calculated a 95% confidence interval for the mean weight of these
In the Northern Hemisphere, dolphins swim predominantly in a counterclockwise direction while sleeping. A group of researchers wanted to know whether the opposite was true for dolphins in the
Just how slippery are banana peels on the floor? “Slipperiness” can be measured by the frictional coefficient. A small value for the coefficient indicates less friction (more slippery) than a
Male koalas bellow during the breeding season, but do females pay attention? Charlton et al. (2012) measured responses of estrous female koalas to playbacks of bellows that had been modified on the
Pit vipers (including rattlesnakes) have a pit organ located halfway between their eyes and nostrils. These organs detect the body heat of unlucky warm-blooded prey (mammals), but the snakes also use
Hurricanes Katrina and Rita caused the flooding of large parts of New Orleans, leaving behind large amounts of new sediment. Before the hurricanes, the soils in New Orleans were known to have high
Refer to Assignment Problem 22. In the same study, Zahran et al. (2010) also measured the lead concentration of blood (in μg/dl) of children living in the 46 areas both before and after the
In Seychelles warblers, young adult females known as subordinates sometimes hang around the territories of older birds. Sometimes these subordinates help feed the offspring of the older birds, and
The evolution of blind cave forms of the fish Astyanax mexicanus is associated with large reductions in the amount of time spent sleeping. The eyed, surface forms sleep about 800 minutes per 24-hour
Without external cues such as the sun, people attempting to walk in a straight line tend to walk in circles. One idea is that most individuals have a tendency to turn in one direction because of
Functionally important traits in animals tend to vary little from one individual to the next within populations, possibly because individuals that deviate too much from the mean die sooner or leave
Global warming is causing many species living on mountain slopes to shift their elevational ranges upward. Is the vertical extent of their ranges (the difference between the upper limit and the lower
Calculation practice: Paired t-test. Can the death rate be influenced by tax incentives? Kopczuk and Slemrod (2003) investigated this possibility using data on deaths in the United States in years in
For each of the following scenarios, the researchers are interested in comparing the mean of a numerical variable measured in two circumstances. For each, say whether a paired t-test or two-sample
Dung beetles are one of the most common types of prey items for burrowing owls. The owls collect bits of large mammal dung and leave them around the entrance to their burrows, where they spend long
In garter snakes, some males emerging from overwintering dens mimic females by producing female pheromones. Males might mimic females to warm up: males tend to emerge sooner than females and warm up
The astonishing diversity of cichlid fishes of Lake Victoria is maintained by the preferences of females for males of their own species. To understand how the species arose in the first place, it is
Spot the flaw. Bluegill sunfish, a species of freshwater fish, prefer to feed in the open water in summer, but, in the presence of predators, they tend to hide in the weeds near shore. A study
In most election years since 1960, a televised debate between the leading candidates for president has been influential in determining the outcome of the U.S. election. One analysis of the
Ostriches live in hot environments, and they are normally exposed to the sun for long periods. Mammals in similar environments have special mechanisms for reducing the temperature of their brain
Most bats are very poor at walking, but the vampire bat is an exception. It is not clear why bats are poor walkers from a mechanical perspective, although a leading hypothesis has been that their
When producing a 95% confidence interval for the difference between the means of two groups, under what circumstances can a violation of the assumption of equal standard deviations be ignored?
Calculation practice: two-sample t-test. When your authors were growing up, it was thought that humans dreamed in black and white rather than color. A recent hypothesis is that North Americans did in
Calculation practice: Confidence interval for the difference between two means. Return to the data about the percentage of dreams in color as a function of age from Practice Problem 2. Determine a
The males of stalk-eyed flies (Cyrtodiopsis dalmanni) have long eye stalks. The females sometimes use the length of these eye stalks to choose mates. (See Example 11.2.) Is the male’s eye-stalk
Fruit flies, like almost all other living organisms, have built-in circadian rhythms that keep time even in the absence of external stimuli. Several genes have been shown to be involved in internal
Researchers studying the number of electric fish species living in various parts of the Amazon basin were interested in whether the presence of tributaries affected the local number of electric fish
Assignment Problem 21 from Chapter 11 discussed the relatedness of subordinate males to breeding females in the Seychelles warbler. Five subordinates that did not help feed the offspring of the older
Weddell seals live in the Antarctic and feed on fish during long, deep dives in freezing water. The seals benefit from these feeding dives, but the food they gain comes at a metabolic cost. The dives
A baby dolphin is born into the ocean, which is a fairly cold environment. Water has a high heat conductivity, so the thermal regulation of a newborn dolphin is quite important. It has been known for
Hyenas, famously, laugh. (The technical term used by hyena biologists is “giggle.”) Mathevon et al. (2010) investigated the information content of hyena giggles. In one analysis, they compared
Does holding a weapon increase your aggressiveness afterward in other situations? Klinesmith et al. (2006) investigated this question by assigning 30 male college students to one of two groups. One
Rutte and Taborsky (2007) tested for the existence of “generalized reciprocity” in the Norway rat, Rattus norvegicus. That is, they asked whether a rat’s willingness to help another individual
Attwood et al. (2012) measured whether the time taken to drink a beer was influenced by the shape of the glass in which it was served. Participants were given 12 oz. (about 350 ml) of chilled lager
Spot the flaw. There are two types of males in bluegill sunfish. Parental males guard small territories, where they mate with females and take care of the eggs and young.Cuckolder males do not have
Spinocerebellar ataxia type 1 is a neurodegenerative disease marked by the gradual loss of motor skills and culminating in early death. It is caused by an expanded CAG repeat in the coding region
Rising atmospheric CO2 and higher tree mortality associated with climate change have been hypothesized to drive increases in the abundance of lianas (climbing woody vines) in tropical forests.
Females of many animals can recognize their own offspring by voice. But how long does this vocal memory last? Briefer et al. (2012) tested the responses of mother goats to their offspring 11 to 17
Individuals with sleep apnea have pauses in their breathing while sleeping that disrupt their normal sleep. A didgeridoo instructor noticed that several of his students reported sleeping better after
Spot the flaw. A recent paper in the research publication Nature examined how fungi cause negative density dependence in plants—the tendency for high plant density to negatively affect plant
Conservation efforts include reintroduction of species into the wild from captive breeding programs. Leung et al. (2018) “rewilded” mice from the inbred laboratory strain of mouse, C57BL/6, that
Calculation practice: Confidence interval for the mean using log transformation. Refer to Practice Problem 19 in Chapter 10. Health spending per person from a random sample of 20 countries is given
Women with mutations in their BRCA1 or BCRA2 genes (“carriers”) represent about 0.5% of the U.S. population (Malone et al. 2006). Women who are carriers have an 80% chance of developing breast
Calculation practice: The sign test. Female goldeneyes (a kind of duck) lay eggs in other females’ nests, in addition to the eggs they produce and raise in their own nests. One advantage to a
Some genera have far more species than others. Is this just luck, or have some genera hit upon a “key innovation” that gives them a benefit and allows more species to accumulate? One possible key
Some researchers bought a new microgram scale. Before using it for new experiments, they wanted to ensure that the readings on the scale were accurate. They obtained a 10-μg standard weight,
Calculation practice: Mann–Whitney U-test. Recycling paper has some obvious benefits, but it may have unintended consequences. For example, perhaps people are less careful about how much paper they
The four graphs shown below are normal quantile plots for four different data sets, each sampled randomly from a different population. For each graph, say whether the distribution is close to a
In the early days of genetics, scientists realized that Mendel’s laws of segregation could be used to predict that the second generation after a cross between two pure strains (the F2 ) ought to
For each of the following sets of numbers, log-transform and calculate the sample mean and 95% confidence interval of the population mean. If that is impossible, say why it is
Below are frequency distributions of a variable in four hypothetical populations.a. For each graph (i through iv), say whether the distribution appears to be a normal distribution.b. For each
The males of some cichlid fish species are infertile until a few days after they become the socially dominant male in the presence of females. Males without a territory (and therefore without a hope
When intruding male lions take over a pride of females, they often kill most or all of the infants in the group. This reduces the time until the females are again sexually receptive. This infanticide
Every year Britain has a No Smoking Day, when many people voluntarily stop smoking for a day. No Smoking Day occurs on the second Wednesday of March each year. Waters et al. (1998) used this event to
The skin of the rough-skinned newt, Taricha granulosa, stores an extremely poisonous neurotoxin called tetrodotoxin (TTX). In some geographical areas, garter snakes, a newt predator, have evolved
In the women’s tennis finals at Wimbledon, the match winner is the first player to win two sets. Sets continue one after the other until there is a winner and loser; there are no ties. If one woman
The four graphs on the next page are all based on random samples with more than 100 individuals. The red dots represent sample means.a. Assume that the error bars extend two standard errors above
Vertebrates are thought to be unidirectional in growth, with size either increasing or holding steady throughout life. Marine iguanas from the Galápagos (see the photo on the first page of this
Red-winged blackbird males defend territories and attract females to mate and raise young there. A male protects nests and females on his territory both from other males and from predators. Males
Mosquitoes find their victims in part by odor, so it makes sense to wonder whether what we eat and drink influences our attractiveness to mosquitoes. A study in West Africa (Lefèvre et al. 2010),
Refer to Practice Problem 15. The accompanying data are the values of mosquito activation (fraction of 50 mosquitos that left the container) recorded on the 25 participants before and after drinking
Males of the Australian butterfly Jalmenus evagoras search for females and mate with them just as the females emerge as adults from the pupae. Multiple males might discover the same female, in which
The pitcher plant from Borneo, Nepenthes rafflesiana, has two kinds of pitchers, upper and lower, that it uses to trap and digest insects. The upper pitchers use fragrance to lure mainly flying
The following are very small data sets of human birth weights (in kg) of either singleton births or individuals born with a twin. We are interested in the difference in mean weight between singleton
For each of the following scenarios, state the null hypothesis and identify the best statistical test to use to answer the question stated. (Don’t try to answer the specific question.)a. Do
Have you ever had the experience that driving somewhere seems to take a really long time, but the trip back home goes faster, even though it is the same distance in reverse? Van de Ven et al. (2011)
One of the founders of modern population genetics, J. B. S. Haldane, was once asked if he could infer anything about God from his study of nature. He replied, “An inordinate fondness for
Kids are often told that they should not crack their knuckles, because otherwise all sorts of terrible things may befall them. It is commonly believed that knuckle cracking leads to arthritis, which
Gesturing is common during human speech. Is this behavior learned via exposure? A measure was made of the number of gestures produced by each of 12 pairs of sighted individuals while talking to
Body size in female northern fur seals (Callorhinus ursinus), measured as total length, is approximately normally distributed with a mean of 124.6 cm and a standard deviation equal to 6.5 cm (Trites
For each of the sets of samples in the accompanying figures (a)–(e), state which approach is best if the goal is to test the difference between the means of group 1 (on the left) and group 2 (on
What feature of an estimate—precision or accuracy—is most strongly affected when individuals differing in the variable of interest are not sampled independently?
The nematode Caenorhabditis elegans is often used in studies of development and genetics. This species is an unusual animal, because most C. elegans individuals are hermaphrodites. That is, each
Of the two scatter plots provided, one represents the real relationship between body size and brain size for 29 species of dinosaur (Hurlburt 1996). The other shows the first permuted data set
In Chapter 3, Assignment Problem 23, you produced a box plot for the following data from Norton et al. (2011). The data are measurements of the amount of time, in seconds, that individual zebrafish
Carotenoids are pigments responsible for much of the red we see in nature. For example, the bright red beak color of the male zebra finch is derived from carotenoids. Carotenoids are also important
The conventional wisdom is that people who play a lot of sports have more sexual partners than those who do not. To test this, a group of French researchers asked two groups of students how many sex
Sockeye salmon swim sometimes hundreds of miles from the Pacific Ocean, where they grow up, to rivers for spawning. Kokanee are a type of freshwater sockeye that spends their entire lives in lakes
The distribution of body size of mosquitoes (as measured by weight) is known to be log-normal (that is, size is normally distributed if logtransformed). The (untransformed) weights of 11 female and 9
Researchers have observed that rainforest areas next to clear-cuts (less than 100 meters away) have a reduced tree biomass compared to rainforest areas far from clear-cuts. To go further, Laurance et
In a study of the Gouldian finch, Griffith et al. (2011) looked at stress caused by having an incompatible mate. There are two genetically distinct types of Gouldian finches, one having a red face
One measure of the exposure of a person to tobacco smoke is the urinary cotinine-to-creatinine ratio (CCR). (Cotinine is formed in the body by breaking down nicotine.) Scientists measured this ratio
Use a six-sided die to make 10 permuted data sets suitable for testing the difference between the medians of the following two groups:a. Write out the 10 permuted data sets.b. Using just these 10
The Milky Way appears as a massive band of stars across the night sky. The nocturnal dung beetle (Scarabaeus satyrus) is known to use this band of illumination for orientation. After sculpting a
T and B lymphocytes are normal components of the immune system, but in multiple sclerosis they become autoreactive and attack the central nervous system. What triggers the autoimmune process? One
The cane toad (Bufo marinus), a large, toxic toad introduced to Australia in 1935, has been rapidly spreading across the continent at over 50 km/year. Are the fastest-moving toads at the leading edge
Dengue infects tens of millions of people annually, resulting in more than 10,000 deaths. The disease is caused by an RNA virus, which is transmitted principally by the mosquito Aedes aegypti.
Despite the voracious habits of army ants, multiple species of invertebrates have managed to penetrate and exploit their societies. For example, the silverfish Malayatelura ponerophila is an insect
The pseudoscorpion Cordylochernes scorpioides lives in tropical forests, where it rides on the backs of harlequin beetles to reach the decaying fig trees in which they live. Females of the species
The vuvuzela captured international attention during the 2010 World Cup in South Africa. In its modern incarnation, the vuvuzela is a plastic horn, about 65 cm long, that can produce a sound loud
Male zebra finches have bright red beaks (see Assignment Problem 18), and experiments have shown that females prefer males with the reddest beaks. The red coloration in the beak comes from a class of
The human immunodeficiency virus (HIV) has a high mutation rate. Many of the mutations that appear are harmful to the virus itself, making it less able to replicate. Are mutations in all genes of the
Identify which goal of experimental design (i.e., reducing bias or limiting sampling error) is aided by the following procedures:a. Using a genetically uniform animal stock to test treatment
Using a coin toss for each unit, assign two hypothetical treatments to eight experimental units.a. Write the sequence of eight assignments you ended up with.b. Did you end up with an equal number
A series of plots were placed in a large agricultural field in preparation for an experiment to investigate the effects of three fertilizers differing in their chemical composition. Before assigning
You read the following statement in a journal article: “On the basis of an alpha level of 0.05 and a power of 80%, the planned sample size was 129 subjects in each treatment group.” State in

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