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Math for journalists

Math for journalists. In general. A lot of stories related to governments are based on numbers. Reporters need to be familiar with basic math to be able to convey the information those numbers represent to readers/viewers. If you aren’t good at math, ask for help. Online tools can be helpful.

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Math for journalists

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  1. Math for journalists

  2. In general A lot of stories related to governments are based on numbers. Reporters need to be familiar with basic math to be able to convey the information those numbers represent to readers/viewers. If you aren’t good at math, ask for help. Online tools can be helpful.

  3. Percentages As proportion of part to whole- Divide the part by the whole- Move the point two spaces right- Add the word “percent” For example- Jones got 215 of the 312 votes cast- 215 divided by 312 is .6891- Jones got 68.9 percent of the vote

  4. Percentages To express change- Determine the base number and the new number.- Find the difference by subtraction.- Divide the difference by the base. For example:- Enrollment last year was 12,310; this year it’s 13,200.- The difference is 890.- 890 divided by 12,310 is .0722- Enrollment has grown by 7.22 percent

  5. For example In a city of 42,000 population, 6,260 residents are Hispanic. What is the city’s percentage of Hispanic residents? Last year, 615 students graduated from the school. This year there were 589 graduates. By what percentage have graduates decreased?

  6. Answers 6,260 Hispanic residents divided by 42,000 total population = 0.1490. Move the decimal two places to the right – 14.9 percent. Base number is 615. Difference is 26. Divide 26 by 615 and it equals .0422. Decline is 4.2 percent.

  7. Measures of central tendency The mean (average)- Add the individual numbers- Divide the sum by the number of numbers.- The result is the mean. For example:- Your grades on quizzes are 4.0, 3.7, 3.7, 2.7, 4.0, 3.3- The total of the six grades is 21.4- 21.4 divided by 6 = 3.56

  8. For example Six people are on a bus. Their incomes are $35,000, $79,000, $65,000, $53,000, $27,000 and $39,000. What is their mean income? The six added together equals $298,000. Divide that total by six, and the result is $49,666.

  9. Measures of central tendency The median- Find the middle number- If you’ve got a sample of 21 cases, the median is the number with 10 numbers greater than it and 10 numbers smaller than it.- In even-number sets, average the two in the middle.

  10. Median income on bus $27,000; $35,000; $39,000; $53,000; $65,000; $79,000 Since the number of cases is even, add the two middle cases and divide by 2. $39,000 + $53,000 = $92,000. $92,000 divided by 2 equals $46,000.

  11. Back to the bus Bill Gates gets on the bus. His income is $100 million. Which measure makes more sense to provide a snapshot of who is on the bus – the mean or the median?

  12. Median income with Gates $27,000; $35,000; $39,000; $53,000; $65,000; $79,000; $100,000,000. Middle number is $53,000. If we had used the mean to express the makeup of the bus ridership, we’d say the average person on the bus earned $14,328,285.

  13. Mills in Michigan Mills are the units used by Michigan governments to levy taxes on property. A mill is a tax of $1 on each $1,000 of taxable value of land, buildings and business equipment and machinery. Taxable value can be no more than half of market value.

  14. Millage calculations Choose a representative taxable value, $50,000 for example. Divide it by 1,000. Multiply the result by the millage rate. If a city levies 2.35 mills, the owner of a home with a taxable value of $50,000 would pay $117.50 in taxes.

  15. Surveys The best use of survey technique is to use a sample to represent the whole. A sample will not be representative unless it is truly random. In a random sample, every member of the whole group has an equal opportunity of being chosen.

  16. Convenience samples Convenience samples – the first five people you meet outside the library, for example – are not representative. Their only valid use is to generate good quotes that illustrate points of view determined by other, more valid means. Don’t misrepresent convenience samples as random samples.

  17. Reporting numbers Cite sources for all statistics. Long lists of figures are difficult to read in stories. Charts and graphs may be a better option. Round off numbers usually after two places. For example: $1.35 million rather than $1,349,276. Always double-check your math and verify statistics a source gives you. If you don’t understand the numbers, get an explanation.

  18. Questions?

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