invest_3ed.pdf

# Investigative nature of these materials is that we

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investigative nature of these materials is that we strongly believe that you will better understand and retain the concepts if you build your own knowledge and are engaged in the context. Be sure to also pay attention to the Study Conclusions to see how to effectively convey statistical information and the Practice Problems for testing your understanding. Though you will only scratch the surface of the statistical methods used in practice, you will learn fundamental concepts (such as variability, randomness, confidence, and significance) that are an integral part of many statistical analyses. A distinct emphasis will be the focus on how the data are collected and how this determines the scope of conclusions that you can draw from the data.

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Chance/Rossman, 2015 ISCAM III Investigation A 4 Investigation A: Traffic Fatalities and Federal Speed Limits These first two investigations give you a very brief introduction to some big ideas for the course. Some of you will have seen some of these ideas before and can use the investigations to refresh your memory. Some of the ideas may be new and you will see them again in later chapters. For now, try to focus on the bigger picture of analyzing data and drawing appropriate conclusions. Increases and decreases in motor vehicle fatalities can be monitored to help assess impacts of changes in policy. For example, in 1974, the US Federal government passed the National Maximum Speed Law, capping the speed limit on all interstate roads to 55mph. At the time, the goal was to improve fuel consumption in response to the 1973 oil embargo. However, when Congress repealed this law in 1995, allowing states to raise the legal speed limit, many wondered if that would also lead to an increase in accidents and fatalities. Frieman, Hedeker, and Richter (2009) took data from the Fatality Analysis Reporting System (FARS) to explore this issue, focusing in particular on the repeal of federal speed limit controls on road fatalities. (a) To the right is a portion of Wikipedia ’s “ List of motor vehicle deaths in the U.S. by year data (through 2013) on the number of total motor vehicle deaths in the United States per year. Notice the data are given in a data table : each row represents a different year and the second column is the number of deaths in the U.S. that year. Suggest a research question that you could investigate with the full dataset. (b) From the data provided here, do you see any trend or pattern to how the number of deaths per year is changing? Does this pattern make sense? What other information would you like to consider? A time plot is a natural way to examine how a variable changes over time, but not about how other variables are also changing over the same time period. In particular, there are a lot more drivers on the roads now than in 1899, which is going to impact the number of deaths, so we really should take that into account. Typically, data like this would be scaled in some way, such as dividing by number of vehicle miles traveled by all cars that year or by the population size of the United States that year.
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