Ms. Gilford's Math - Home



Name: ______________________________________3.6&3.7 Practice - Experiments1. Good for the gut??Is fish good for the gut? Researchers tracked 22,000 male physicians for 22 years. Those who reported eating seafood of any kind at least 5 times per week had a 40% lower risk of colon cancer than those who said they ate seafood less than once a week. Based on this study, is it reasonable to conclude that eating seafood causes a reduction in the risk of colon cancer? Explain.2. It pays to be mean??A recent study based on data from three different surveys spanning 20 years found that men who scored below average on “agreeableness” earned, on average, 18% more than those who scored above average. Though the gap was smaller, a similar result was found for women. Based on this study, is it reasonable to conclude that men are likely to earn a higher salary if they act less agreeable? Explain.3. More rain??The changing climate might affect the amount of rain that falls during different seasons. Eighteen plots of open grassland, each with an area 70 square meters, were available for a study. One response variable is total plant biomass produced in a plot over a year. Kenwyn Suttle of the University of California at Berkeley and his coworkers wanted to compare the effects of three treatments: added water equal to 20% of annual rainfall either during January to March (winter) or during April to June (spring), and no added water (control). Explain why it was necessary to include a control group that didn’t get additional water. 4.Getting the teacher to show up?Elementary schools in rural India are usually small, with a single teacher. The teachers often fail to show up for work. Here is an idea for improving attendance: Offer the teacher better pay for good attendance. Give the teacher a digital camera with a tamper-proof time and date stamp, and ask a student to take a photo of the teacher and class at the beginning and end of the day to verify attendance. Will this work? Researchers obtained permission to use 120 rural schools in Rajasthan for an experiment to find out. Explain why it is necessary to include a control group that doesn’t get a financial incentive. 5.Yum, jellyfish!?Research by Andrew Sweetman of Norway’s International Research Institute of Stavanger focused on whether or not deep-sea scavengers consume dead jellyfish. His team lowered platforms piled with dead jellyfish and other platforms piled with dead mackerel more than 4000 feet into Norway’s largest fjord, and they found that hagfish, crabs, and other scavengers consumed the jellyfish in a few hours—faster than they consumed the mackerel. Explain why it was necessary to include platforms containing mackerel in the experiment, even though the study was focused on the consumption of jellyfish. 6.Oils to make us limber??The extracts of avocado and soybean oils have been shown to slow cell inflammation in test tubes. Will taking avocado and soybean unsaponifiables (ASU, i.e., components of the oily mixture) help relieve pain for subjects with joint stiffness due to arthritis? In an experiment, 345 men and women were randomly assigned to receive either 300 milligrams of ASU daily or a daily placebo for three years. Could blinding be used in this experiment? Explain. Why is blinding an important consideration in this experiment? 7.Ultrasounds?Researchers examined the effect of ultrasound on birth weight. Pregnant women participating in the study were randomly assigned to one of two groups. The first group of women received an ultrasound; the second group did not. When the subjects’ babies were born, their birth weights were recorded. The women who received the ultrasounds had heavier babies, on average. a) Why was it necessary to perform an experiment rather than simply asking the women whether or not they had an ultrasound during pregnancy?b) Explain why it was important for the experiment to include a control group that didn’t receive an ultrasound.c) Could blinding be used in this experiment? Explain. Why is blinding an important consideration in this experiment?8. Pricey pizza? The cost of a meal might affect how customers evaluate and appreciate food. To investigate, researchers worked with an Italian all-you-can-eat buffet to perform an experiment. A total of 139 subjects were randomly assigned to pay either $4 or $8 for the buffet and then asked to rate the quality of the pizza on a 9-point scale. Subjects who paid $8 rated the pizza 11% higher than those who paid only $4.62 Describe how the researchers could have randomly assigned the subjects to treatments using (a) identical slips of paper and (b) a random-number generator.9. Vitamin D and asthma?Researchers randomly assigned 408 adults with persistent asthma to take one of two treatments: an inhaled medicine with a vitamin D supplement or the inhaled medicine with a placebo.?Results: After seven months, the vitamin D users were no less likely to experience reduced air flow, hospitalization, or the need for additional medicine. a) Identify one variable that researchers kept the same in this experiment.b) Explain how keeping this variable the same helps prevent confounding. ................
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