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Murder Rates Up! Or just up?

Rhetoric in an election season is of course filled with exaggeration, but it is not just the candidates who engage in hyperbole.  The article, Murder Rates Rose in a Quarter of the Nation’s 100 Largest Cities, uses  FBI crime data to explore whether the real increase in homicides in our nation’s largest cities was indeed evidence that “crime is out of control” across the country.  In fact, half the homicide increase came from just 7 cities: Baltimore, Chicago, Cleveland, Houston, Milwaukee, Nashville and Washington.


My students enjoyed discussing the different ways to spin the crime data, and it gave me another opportunity to quiz their facility with ratios.  The homicide rate per 100,000 sounds like a self-explanatory statistic, but the article mixes absolute numbers with rates causing fun confusion.  Question #1 on the quiz caused lots of problems.  In addition, there was an interesting argument put forth attributing the surge in Baltimore homicides to the looting of drugs from pharmacies after the Freddie Gray riots.  This influx of drugs onto the market destabilized the gang market for narcotics, creating a power struggle.  Great quantitative reasoning involved in analyzing this argument!

Q3 Homicides

  1. The article, Murder Rates Rose in a Quarter of the Nation’s 100 Largest Cities, has lots of different ways to represent the same data!
    1. They say that Baltimore had the largest increase in homicides, 133 more than 2014, but the graphic below seems to be indicating only 55 homicides for Baltimore in 2015? Explain how these statistics are not contradictory.
    2. They tell us that Chicago had the most homicides – 488 in 2015 – far more than the 352 in NYC, which has 3 times the people. Use the graphic below to determine the populations of BOTH Chicago and New York City.
    3. Compute the ratio of homicides in Chicago in 2015 to homicides in NYC in 2015, and scale the second quantity to 1. Then compute the ratio of homicide rate for Chicago in 2015 to the homicide rate in NYC in 2015, scale second quantity to 1.
    4. Write a sentence for each of the ratios (2 sentences) you computed in part 3.
  2. In DLS Joel Best discusses organizational practices and how choices must be made that affect the statistics computed. Our article mentions that “most of the homicides in Baltimore were connected to the drug trade.”  Discuss how organizational practices could impact the creation of a new statistic for “drug related homicides”.
  3. Joel Best discusses how big numbers confuse people.
    1. Compute how long 1 thousand seconds is in minutes.
    2. Compute how long 1 million seconds is in days.
    3. Compute how long 1 billion seconds is in years.
    4. Compute how long 1 trillion seconds is in years.
    5. Complete the following analogy: A penny is to $10,000 as _________ is to $1 trillion. The value you just put in the blank is like a penny to the U.S. government’s budget.





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