3.6 - 3.7 Observations Studies and Experiments

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 five times per week had a 40% lower risk of colon cancer than those who said they eat seafood less than once a week. Based off the study, is it reasonable to conclude that eating seafood causes a reduction in the risk of colon cancer? Explain.

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Changing climate might affect the amount of rain that falls during different seasons. 18 plots open grassland, each with an area 70 m², 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.

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CCSS.HSS.IC.B.5

The extracts of avocado and soy bean oil‘s have been shown to slow cell inflammation in test tubes. Will taking avocado and soy bean unsaponifiables 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 mg of ASU daily or daily placebo for three years. Could blinding be used in this experiment? Explain. Why is blinding an important consideration in this experiment?

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Will cash bonuses speed the return to work of unemployed people? Estate department of labor notes that last year at 60% of people who file claims for unemployment insurance found a new job within 15 weeks. This year, the state offers $500 to people filing unemployment claims if they find a job within 15 weeks. The percent increase is a 77%. What flaw in the design of this experiment makes it impossible to say if the bonus really caused the increase? Explain.

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The cost of a meal might affect our customers evaluate and appreciate food. To investigate, researchers worked with an Italian all you can eat buffet to perform an experiment. A total of 339 subjects were randomly assigned to pay either four dollars or eight dollars for a buffet and then asked to rate the quality of the pizza on a nine point scale. Subjects who paid eight dollars rated the pizza 11% higher than those who paid only four dollars. Explain the purpose of the random assignment in this experiment.

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In an experiment to determine how calories and beverages effects appetite, researchers randomly assigned volunteers to one of four treatments: 150 cal of apple slices, 150 cal of applesauce, 150 cal of apple juice, and 150 cal of apple juice with added fiber. 15 minutes later, researchers provided each participant with a large bowl of pasta and measured how many calories each person consumed. The apple slice group 8 190 fewer calories, on average, compared to the other three groups. Identify one variable that researchers kept the same in this experiment. Other than to avoid confounding, explain another benefit of keeping this variable the same.

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CCSS.HSS.IC.B.5