Final exam study guide: Practice exam 1

Here is the second part of the study guide for the final exam, some practice questions. Before you look at these, you should look at the first part of the study guide. To see the correct answer to a question, click on the "Answer" button. Don't bother typing your answer into the box, it won't do anything.

Where two correct answers are shown for these practice questions (such as chi-squared or G-test of independence), you must only write down one on the actual exam.

  1. You do a pilot study on 9 people on range-of-motion of the knee, and the average value for knee flexion is 138 degrees, with a standard deviation of 15.6 degrees and a standard error of the mean of 5.2 degrees. You plan to do a larger study of knee flexion in 900 people. How do you think the standard deviation and standard error of your larger sample will compare to that from your pilot study?
  2. You want to know whether left-handedness has become more common in the last 70 years. You survey 1,200 first-grade students and 1,050 residents of nursing homes (all about 80 years old) and ask which hand they write with. What test should you use?
  3. You want to know whether dog owners tend to pick dogs of the same sex as the owner. Of 25 single female dog owners, 15 have female dogs and 10 have male dogs. Of 20 single male dog owners, 7 have female dogs and 13 have male dogs. What test should you use?
  4. William the Wildlife Biologist wants to know whether the number of polar bears in Alaska has been decreasing. He has data for the total number of polar bears in Alaska, collected once each year for the past 30 years. He plots a graph with the year on the X-axis and the total number of polar bears on the Y axis and analyzes the data with linear regression/correlation. What makes William's choice of technique incorrect?
  5. You have been observing a large troop of monkeys in the Philadelphia zoo. Some of the monkeys were born in the Philadelphia zoo, and some of the monkeys were born elsewhere and then brought to Philadelphia. By careful observation of their social interactions, you have figured out the dominance heirarchy: which monkey is dominant over all, which monkey submits only to the most dominant, etc., all the way down to the poor monkey that submits to every other monkey. You want to know whether monkeys born at the Philadelphia zoo tend to have higher dominance than monkeys brought from other zoos. What test should you use?
  6. You want to know whether running 4 times a week causes the resting heart rate to decline. You measure the heart rate of 100 people, then make them run 20 minutes a day, 4 days a week, for three months. Then you measure their heart rate again. You calculate the change in heart rate for each person, and plot these differences on a histogram; it looks highly non-normal. What test should you use?
  7. You want to know whether the size of the hippocampus, a structure in the brain, is different in rats with different mental experiences. You plan to use Model I one-way anova and the Tukey-Kramer technique to compare the average hippocampus volume for rats that spend five hours a day learning to run through mazes, rats that spend five hours a day watching TV, rats that spend five hours a day listening to Mozart, and rats that do none of these. You expose 50 rats to each treatment for a month, then dissect out their brains and measure the hippocampus volume. What should you do next?
  8. Because of the long tail feathers, male swallows mount the females from either the right or the left. You want to know whether they have a preference for one side, so you observe 17 pairs of mating swallows. Four males mount from the right side, while 13 mount from the left. What test should you use?
  9. You want to know whether the breakfast you give homing pigeons on the day of a race affects their flying speed. You randomly choose four groups of pigeons, with 5 males and 5 females in each group, and you give one group bird seed, one group crickets, one group corn, and one group gets yogurt. You measure the flying speed and analyze the data using a two-way anova with replication. The P-value for the effect of sex is 0.42, the P-value for the effect of food is 0.008, and the P-value for the interaction term is 0.002. What can you conclude about the effect of breakfast on the flying speed of pigeons?
  10. You want to know whether tearing the anterior cruciate ligament (ACL) in the knee leads to long-term weakness in the quadriceps (front of the thigh) muscle. You measure quadriceps strength in 14 female college volleyball players and 10 male volleyball players, all seniors, who tore their ACL during their first year of college, then were able to play for their sophomore through senior years. You also measure quadriceps strength in 20 female and 17 male volleyball players who never tore their ACL. What test should you use?
  11. You want to know whether taking the supplement resveratrol, a natural substance found in red wine, can increase HDL levels (the "good cholesterol") in the blood. You measure the HDL levels in a group of 48 people, give them all the supplement for twelve weeks, then measure their HDL again. What test should you use?
  12. Glacier-Waterton International Park is in Montana and Alberta. While backpacking through the park, you see 8 black bears and no grizzly bears in the Montana side of the park; after crossing the border into Canada, you see no black bears and 6 grizzly bears in the Alberta side of the park. You want to know whether there's a difference between the two parts of the park in the relative abundance of the two bear species. What test should you use?
  13. You want to know whether there is a relationship between weight and alcohol intake in college students. You weigh 50 students and ask them how much alcohol they drink in a week. What test should you use?
  14. You've found that heavier college students drink more alcohol; now you want to know whether students with different extracurricular activities drink different amounts. You find 20 male students who do lab research, 25 male students who are varsity athletes, 17 male students who are in fraternities, and 29 male students who do none of these activities. You exclude students who are involved in more than one activity. You weigh each student and ask them how much alcohol they drink each week. What test should you use?
  15. You want to know whether tryptophan, an amino acid found in relatively high concentrations in turkey, really makes people sleepy. You make some pills with 7 different amounts of tryptophan and have a friend give you a random pill at dinnertime every day for a week. One hour after each dinner, you sit in a comfortable chair and watch a "Law and Order" rerun. Your friend records how many minutes you stay awake, and at the end of the week, your friend tells you which pill you took on each day. What test should you use?
  16. You want to know whether male athletes who take steroids have enlarged prostates. At a weightlifters' convention, you find 43 men who admit to taking steroids and 27 men who claim they have never taken steroids. You measure the size of each man's prostate using ultrasound. Because you expect the prostate to get larger with age, you also record the age of each subject. What test should you use?
  17. You want to know whether there is any genetic variation for barkiness in miniature schnauzer dogs. You obtain 7 litters of miniature schnauzers, raise them under similar conditions, then record how many times each dog barks when a stranger approaches it. You do this once for each dog. What test should you use?
  18. You are trying to see whether the genes Jam-1 and Pax-6 are genetically linked in zebrafish. You cross individuals who are heterozygous for visible, dominant mutations at both genes, and you get 1600 offspring. If the two genes are unlinked, you'd expect 100 fish that were normal/normal, 300 that were normal at Jam-1 and mutant at Pax-6, 300 that were mutant at Jam-1 and normal at Pax-6, and 900 that were mutant/mutant. What test should you use?
  19. You want to know whether the presence of the malaria parasite (Plasmodium) in mosquitoes affects the West Nile virus. You collect 1200 mosquitoes. Half of them contain Plasmodium and one-third contain West Nile virus, so your null expectation is that one-sixth (200) of the mosquitoes will have both Plasmodium and West Nile virus. Instead, you find that only 148 mosquitoes have both. What test should you use?
  20. You are planning a big study on hopping ability in people who've injured their anterior cruciate ligament, and you want to know whether you're going to have to control for height when comparing hopping distance. You get 34 volunteers, measure their height, and measure how far they can hop on one leg. What test should you use?
  21. Killifish have pigmented cells on their dorsal fin called melanopores that disperse and aggregate during certain circumstances. You want to know whether predators affect the melanopore index (darkness) of killifish. You have three tanks with killifish and no predators, three tanks with killifish and a dogfish shark, three tanks with killifish and a heron, and three tanks with killifish and a seal. After one hour, you take 12 killifish from each tank and measure the melanopore index on 5 randomly chosen scales from each fish. What test should you use?
  22. You have collected samples of soil from five sites in a marsh in Lewes, DE. You want to know which site has the highest nitrogen fixation rate. You divide each soil sample into 10 flasks and measure the acetylene reduction activity (a measure of nitrogen fixation) in each flask. What test should you use?
  23. Your lab is studying three different species of pathogenic bacteria, and you want to know which of four detergents is best for cleaning up. You put 1 ml of a culture of species A on a lab bench, let it dry, then wipe it with a 1% solution of detergent X. Then you touch a sterile agar plate to the spot on the lab bench, then count the colonies after 24 hours. You do this 5 times for each bacterium with each detergent. What test should you use?
  24. You are studying the effect of diet and exercise on longevity. You put 100 mice in individual cages. Each cage has an exercise wheel connected to a recorder that measures the time that the mice spends running on the wheel. You keep the feeding trough full of food and record how much food the mouse eats. You know when each mouse was born, and you record the day that each mouse dies. What test should you use?
  25. Fiddler crabs have pigment cells called melanopores; you want to know whether they use them for camoflauge. You put 50 individually tagged fiddler crabs on a black background for 24 hours, then measure the amount of light reflected off their carapace. You then put the crabs on a white background for 24 hours and measure the amount of light reflected off each crab's carapace. A few crabs show a huge decrease in absorbance, but most show a slight increase or decrease. What test should you use?
  26. You want to know whether 12 clonal strains of E. coli bacteria differ in catabolic activity. You grow three lines of each strain for 2,000 generations, then take three samples of each line and measure the catabolic activity of each sample. What test should you use?
  27. You want to know whether tryptophan, an amino acid found in relatively high concentrations in turkey, really makes people feel sleepy. You make some pills with 7 different amounts of tryptophan and have a friend give you a random pill at dinnertime every day for a week. One hour after dinner, you write some notes about how sleepy you feel. At the end of the week, you look at the notes and put the days in order, from sleepiest to least sleepy; you then have your friend tell you which pill you took on each day. What test should you use?
  28. You are studying the effect of age on running speed, trying to predict the age at which people run the fastest. You know that small children and old people run relatively slowly compared to youngish adults. You time 769 girls and women, ages 5 to 75, in the 50-meter dash. What test should you use?
  29. You want to know whether eating turkey really makes people sleepy. At a large Thanksgiving dinner, 10 people eat turkey, while 7 people are vegetarians and have tofu instead. Both the carnivores and the vegetarians eat stuffing, mashed potatoes, cranberry sauce, green bean casserole, and pumpkin pie. After dinner, you show a video of your trip to Nebraska, and you record the order in which the people fall asleep. What test should you use?
  30. You know that adding fertilizer to poor-quality soil increases the yield of tomatoes, but too much fertilizer is bad for the plants. You want to model the relationship between fertilizer amount and yield of tomatoes, so you can choose the optimum amount of fertilizer to use. You set up 20 experimental 10-m2 plots, with a different amount of fertilizer on each, and count the number of tomatoes produced in each plot. What test should you use?
  31. You've always wanted to win the Mid-Delmarva Herpetological Society's annual Eastern Racer race, where herpetologists have one hour to find an Eastern Racer snake (Colubor constrictor), which are then numbered and raced on a snake racetrack. You've confident that you can find several snakes in one hour, but you won't have time to test their speed, so you want to be able to predict which will be the fastest snake. In the week before the race, you capture 20 snakes, measure their length and weight, then measure their top slithering speed on a snake treadmill. What test should you use?
  32. When a click beetle is on its back, it rapidly flexes its body with an audible "click," flipping itself into the air and hopefully landing right-side-up. You want to know whether this flipping is random or whether the beetles tend to land on their feet. You catch a click beetle, put it on its back, and watch it click. You repeat this 12 times. The beetle lands on its feet 8 times and on its back 4 times. What test should you use?
  33. You want to know whether a common polymorphism (G or A in the DNA sequence) in the promoter of the uncoupling protein 2 gene is involved in type II diabetes. You measure the insulin sensitivity index (low values are associated with diabetes) in 5000 volunteers: 823 with the G/G genotype, 2732 with the G/A genotype, and 1545 with the A/A genotype. What test should you use?
  34. You've been hired by a turkey company, which wants to know, "Do male turkeys have the same fat content as female turkeys of the same size, or are they different?" You get 20 male and 20 female turkeys of a variety of sizes, weigh them, and measure the fat content of each. You analyze the data using ancova (since fat content might also be associated with weight). The P-value for the difference in slopes is 0.031, while the P-value for the difference in intercepts is 0.007. What answer do you give to the turkey company?
  35. You have taught your dog, Princess Fleabag, a new trick, balancing a doggie treat on her nose and catching it. You want to know whether the position of the treat on her nose affects her ability to catch it. You put the treat on the tip of her nose 20 times, and on the base of her nose, near her eyes, 20 times, and record how many times Princess Fleabag catches the treat from each position. What test should you use?
  36. You want to know whether prostate cancer cells that do not express active RhoC-GTPase adhere to bone marrow endothelial cells at the same rate as normal prostate cancer cells. You treat both kinds of cancer cells with a fluorescent substance and prepare a 24-well microtiter plate with endothelial cells in each well. You add the fluorescent cancer cells to the wells (12 wells with RhoC-GTPase- and 12 wells with RhoC-GTPase+ cells), wait half an hour, then wash away all the unattached cancer cells. You then measure the fluorescence in each well. What test should you use?
  37. You want to know the effect of temperature on the growth of snails. You have 10 fish tanks at 10 C and 10 fish tanks at 30 C, and you put 5 snail eggs in each tank. After 6 months, you measure the length of each snail.

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This page was last revised December 4, 2013. Its URL is http://udel.edu/~mcdonald/statstudy3b.html