Researchers have linked an increase in the incidence of breast cancer in Italy t

Question

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 age 40 at the time. Fifteen of the women had developed breast cancer at an unsually young average age of 45. Medical records showed that they had heightened concntrations of dioxin in their blood and that each tenfold increase in dioxin level was associated with a doubling of the risk of breast cancer. (Source: *Science News*, Aug. 3, 2002). You should write only 1 or 2 sentences for each of the following parts! a) Was this an observational study or an experiment? SOLUTION: If you said this was an observational study, do parts b) through e) below. If you said this was an experiment, do parts t) through z) below. b) (Only do this if you said this was an observational study in part a): Was this a retrospective study or a prospective study? SOLUTION: c) (Only do this if you said this was an observational study in part a): Who were the subjects studied and how were they identified? SOLUTION: d) (Only do this if you said this was an observational study in part a): What is the parameter of interest? SOLUTION: e) (Only do this if you said this was an observational study in part a): Discuss the nature and scope of the conclusions that can be reached from this study. SOLUTION: t) (Only do this if you said this was an experiment in part a): Who were the subjects studied? SOLUTION: u) (Only do this if you said this was an experiment in part a): What are the factor(s) in the experiment, and how many levels are there for each factor? SOLUTION: v) (Only do this if you said this was an experiment in part a): What is the number of treatments? SOLUTION: w) (Only do this if you said this was an experiment in part a): What is the response variable? SOLUTION: x) (Only do this if you said this was an experiment in part a): Was the design completely randomized? Was blocking used? SOLUTION: y) (Only do this if you said this was an experiment in part a): Was blinding used? If so, single blinding or double blinding? SOLUTION: z) (Only do this if you said this was an experiment in part a): Discuss the nature and scope of the conclusions that can be reached from this study. SOLUTION: #### SDM4 13.46 (The train) To get to work, a commuter must cross train tracks. The time the train arrives varies slightly from day to day, but the commuter estimates he'll get stopped on about 15% of work days. Let's assume that the events of being stopped on different days are independent. Define the events A = stopped on Monday, B = stopped on Tuesday, C = stopped on Wednesday, D = stopped on Thursday, and E = stopped on Friday. During a certain 5-day work week, what is the probability that he: a) gets stopped on Monday and again on Tuesday SOLUTION: b) gets stopped for the first time on Thursday SOLUTION: c) gets stopped every day SOLUTION: d) gets stopped at least once during the week? (**Hint**: consider using the complement rule) SOLUTION: #### Language and Poverty in the United States The American Community Survey is an ongoing survey that provides data every year to give communities the current information they need to plan investments and services. The 2010 American Community Survey estimates that 14.6% of Americans live below the poverty line, 20.7% speak a language other than English (foreign language) at home, and 4.2% fall into both categories. Define the events A = a randomly selected American lives below the poverty line and B = a randomly selected American speaks a language other than English at home. a) Are living below the poverty line and speaking a foreign language at home disjoint? SOLUTION: b) What is the probability that a randomly selected American lives below the poverty line or speaks a language other than English at home (or both)? SOLUTION: c) What is the probability that a randomly selected American lives below the poverty line and only speaks English at home? SOLUTION: d) Is the event that someone lives below the poverty line independent of the event that the person speaks a foreign language at home? SOLUTION: #### SDM4 14.28 (Sick cars) Twenty percent of cars that are inspected have faulty pollution control systems. The cost of repairing a pollution control system exceeds $100 about 40% of the time. When a driver takes their car in for inspection, what's the probability that they will have to pay more than $100 to repair the pollution control system? SOLUTION:

Explanation / Answer

Part (a)

This was an observational study because it only identified existing 981 women who lived near the site of the accident and were under age 40 at the time and studied their medical records and it did not involve any planned experiment or tests. ANSWER

Part (b)

This was a retrospective study since it only studied the existing past records. ANSWER

Part (c)

The subjects studied were 981 women who lived near the site of the accident and were under age 40 at the time and they were identified from existing medical records. ANSWER

Part (d)

The parameter of interest is the relation between breast cancer and dioxin released by an industrial accident. ANSWER

Part (e)

The nature and scope of the conclusions that can be reached from this study.

This is a relational study and its conclusions could throw light on the connection between dioxin release and cancer. It is possible that the study does not establish an exact relationship, but it is almost sure to give certain lead for further probe.

ANSWER

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