Observational Studies and Experiments Directions: Read each brief statistical report and identify the following depending on whether the scenario is a survey, observational study, or experiment: If it was an observational study, identify (if possible): a. whether it was retrospective or prospective, b. the subjects studied and how they were selected. c. what we can conclude from the study If it was an experiment, identify if possible) a the subject studied b. the factor in the experiment and the number of levels for each. c. the number of treatments d. the response variable measured e. what we can conclude from the study 1. Researchers have linked an increase in the incidence of breast cancer in Italy to dioxin released by an industrial accident in 1976. The study identified 981 women who lived near the site of the accident and were under the age of 40 at the time. Fifteen of the women had developed breast cancer at an unusually young average age of 45. Medical records showed that they had heightened concentrations of dioxin in their blood and that each tenfold increase in dioxin level was associated with a doubling of the risk of breast cancer. (Science News, Aug. 3, 2002) 2. Is diet or exercise effective in combating insomnia? Some believe that cutting out dessert can help alleviate the problem, while others recommend exercise. Forty people suffering from insomnia agreed to participate in the month-long test. Half were randomly assigned to the special no-desserts diet; the others continued desserts as usual. Half of the people in each of the groups were randomly assigned to an exercise program, while the others did not exercise. Those who ate no desserts and engaged in exercise showed the most improvement 3. A research organization designed an experiment to test the effects of an educational TV show and its website on the learning of mathematical reasoning among upper elementary school students. The website had two type of activities: basic and advanced. The available students were randomly assigned to watch the show or not. Among these same students. some improvement 3. A research organization designed an experiment to test the effects of an educational TV show and its website on the learning of mathematical reasoning among upper elementary school students. The website had two type of activities: basic and advanced. The available students were randomly assigned to watch the show or not. Among these same students, some were randomly assigned to skip the website while others were randomly assigned to use the website. Among the latter. some were randomly assigned to do only the basic activities and the rest to do both the basic and advanced activities. Then, students took a variety of mathematical reasoning tests. 4. In a Time Magazine Article "Please, Please, Go to Sleep" it was noted that about 60% of a child's growth hormone is secreted during sleep, so it is believed that a lack of sleep in children might stunt growth. a. What is the response variable and what is the explanatory variable in this association? b. Explain why it is difficult (and unethical) to get objective verification of this possible causal relationship c. How would this work as an observational study? Describe how the study would be implemented. Would we still be able to conclude a causal relationship? What would be able to conclude from an observational study