Newspaper math

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Newspaper math

• Taking the numb out of numbers
• by Joe Grimm
• Detroit Free Press

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Well, if I called the wrong number, why did
you answer the phone?

• -- James Thurber

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Crunch or be crunched(dont just sit there)

• Consistency
• Context
• Completeness
• Care
• Conversions

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Consistency

• John Smith, who survived World War II and the
  Korean conflict, died of an accidental gunshot
  wound Thursday. He was 67. Smith was survived by
  four sons John Jr., George, Mark and Williams,
  and a daughter, Berry Lords.

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Context (know your numbers)

• Detroit population
• Michigan population
• U.S. population
• Comerica Park
• Ford annual earnings
• State budget
• Federal spending, 2000

• 1 million
• 9 million
• 275 million
• 200-300 million
• 7 billion
• 35 billion
• 1.7 trillion

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Context II Make it meaningful

• The value of (Gates) stock reached an
  incredible 81.4 billion. To put that in
  perspective Thats 209,357,326 14-ounce tins of
  Beluga caviar or 513 Boeing 747s, or nearly the
  gross domestic product of Israel. In other words,
  its a lot more money than most people can
  fathom.
• -- USA Today

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Thrill of a trill ...

• Say you had the chance to blow about 2 trillion.
  You could
• Buy 26,317,520 Jaguar XK8 convertibles -- nearly
  three for everyone in Michigan.
• Pay off credit card debt for EVERYONE in the
  United States -- four times!
• Give 7,272 to each of the 275 million people in
  the United States.

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Completeness(Raw numbers AND processed)

• A 7 percent increase in MSUs budget
• Putting 1,000 more police on U.S. streets
• One million workers wear headphones
• Sanitation workers get a 10 percent raise
• The hospital cut 200 workers
• Auto Show attendance is up 12 percent

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Use care

• Does it make sense?
• Is it million or billion?
• Is that an increase of 2 percent, or 2 percentage
  points?
• Watch superlatives
• Check dates, phone numbers

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Conversions

• Start by estimating
• Weight of a premature baby
• Boiling water
• The distance from Detroit to Chicago
• Then use conversion tables and calculators

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Meet the average JoesJo 45 Joe 40 Bill, 11
Peg Pete, 7

• Average age 22
• Median age 11
• Mode 7
• What does this imply about the average wage at
  Microsoft?

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Percentage

• Percent simply means per hundred.
• That means a percent can be expressed as anything
  divided by a hundred.
• We generally dont have trouble with a
  percentage 27 percent of students have
  tattoos.
• The difficulty is with percent change

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Percent increase

• Three numbers are under consideration
• What you start with
• What you end with
• The difference
• Any two will give you the third and the
  percentage

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Lets try one

• What is the percent increase from 50 to 75?
• The difference is 25.
• Divide the difference by the starting number
• 25/50 .5 50
• Answer A 50 percent increase

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Do some on your own(Estimate, calculate, think)

• What is the increase
• from 100 to 200?
• From 40 to 65?
• From 2,800 to 35,000?
• From 9.47 to 12.13?
• From 1.4 million to 1.9 million?

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Percentage decrease

• We still are focusing on the difference between
  before and after.
• We still divide the difference, or the amount of
  the change, by the starting number.
• The only thing that changes is we are starting
  with a larger number, rather than a smaller
  number.

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Lets try a decrease together

• What is the percent decrease from 75 to 50?
• The difference is 25.
• Divide the difference by the starting number
• 25/75 .33 33
• Answer A 33 percent decrease
• (Why wasnt the answer 50 this time?)

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This time, you know the percent

• Calculating percentage changes is easy. Simply
  multiply the beginning number by the percentage.
• Remember, NO increase would be times 1, so a 20
  percent increase would mean you multiply the
  starting number by 1.20.

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Try some increases

• What would a 20 percent increase do to a 800
  paycheck?
• A city with a population of 70,000 grows by 7
  percent
• A state budget of 185,000 goes up by 30 percent.

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Now, try some decreases

• What would a 20 percent decrease do to a 800
  paycheck?
• A city with a population of 70,000 shrinks by 7
  percent
• A state budget of 185,000 goes down by 30
  percent.
• (What about the numbers this time? Why?)