Jane E. Miller, PhD
The Chicago Guide to Writing about Numbers, 2 nd edition.

• Which information to include when reporting a number
– Context
– Units
• Illustrative examples
– Poor/better/best
The Chicago Guide to Writing about Numbers, 2 nd edition.

• For every example or fact (numeric or other), specify:
– When?
– Where?
– Who?
• Everyone?
• Subgroup (by race, age, gender, or some other trait)?
• Without this context, readers can’t
– Interpret the facts correctly.
– Compare them against numbers from other sources.
The Chicago Guide to Writing about Numbers, 2 nd edition.

• Suppose you are comparing two unemployment rates.
• They could legitimately have different values if they are from
– Different times (e.g., 2005 vs. 2015)
– Different places (e.g., New York vs. US as a whole)
– Different groups (e.g., men vs. women)
• Can’t do a good, systematic comparison unless can specify on which “W’s” the rates differ.
The Chicago Guide to Writing about Numbers, 2 nd edition.

• System of measurement
• Scale
• Level of aggregation
The Chicago Guide to Writing about Numbers, 2 nd edition.

• British?
• Metric?
• Other?
The Chicago Guide to Writing about Numbers, 2 nd edition.

• Length in centimeters or meters?
• Weight in grams or kilograms?
• Mortality rate percent, per 1,000 or per
100,000?
The Chicago Guide to Writing about Numbers, 2 nd edition.

• Price per piece or per dozen or per gross?
• Population by census tract or town or county?
• Poverty rates for individuals or families or towns?
The Chicago Guide to Writing about Numbers, 2 nd edition.

• Must compare within a consistent
– System of measurement
• E.g., 1 meter is longer than 2 feet , so can’t just say “2 > 1” without considering different systems of measurement.
– Scale
• E.g., 1 meter is longer than 10 centimeters , so can’t just say “10 > 1” without considering that even though both are metric measurements, the scale is different.
– Level of aggregation
• E.g., $1 per piece is more expensive on a per-unit basis than $10 per dozen , so can’t just say “10 > 1” without considering level of aggregation.
The Chicago Guide to Writing about Numbers, 2 nd edition.

– “ During the 3rd century, the Black Plague killed 25 million people in Europe .”
– “ In 2001 , the average temperature in the New York City area was 56.3
degrees Fahrenheit .”
– “ Median household income was $ 49,445 in the US in
2010 .
– Check:
• When? Where? What? How many? Units?
• Note that the W’s don’t always appear in the same order. Many types of sentence structures are possible.
The Chicago Guide to Writing about Numbers, 2 nd edition.

• Introduce and explain a general principle.
– E.g., “setting the context”
• Illustrate concept with sentences.
– “ Poor ” – doesn’t follow the principle
– “ Better ” – partially follows the principle
– “ Best ” – follows the principle
• Annotate each sentence to show why it is
“poor” or “better.”
• Make abstract ideas concrete.
The Chicago Guide to Writing about Numbers, 2 nd edition.

• Poor: “The height was 27.”
– What are we measuring?
– In what context?
– In what units?
• Better: “The plant measured 27 centimeters tall.”
– Now we have size , units, and “ what ” concept (plant height).
– When? Which plant (e.g., under what conditions)?
• Best: “ Two weeks after germinating , the plant that was watered daily measured 27 centimeters tall .”
– When, what (plant height), which plant, size, and units.
The Chicago Guide to Writing about Numbers, 2 nd edition.

• Poor: “The plant I am talking about was watered daily .
It was measured in centimeters . I measured it two weeks after it germinated. It’s height was 27.
”
– In your rough notes, you might need to write a separate sentence about each W, just to get the information correct.
– Then condense and simplify the W’s into one sentence for a more concise, conversational sentence.
• Better: “ Two weeks after germinating , the plant that was watered daily measured 27 centimeters tall .”
– All of the W’s and units in one sentence.
– With practice, you will get closer to this version on your first try.
The Chicago Guide to Writing about Numbers, 2 nd edition.

• Poor: “ The first day after germinating , the plant that was watered daily was 0.7
centimeters tall . The third day after germinating , the plant that was watered daily . . . Two weeks after germinating , the plant that was watered daily measured 27 centimeters tall .”
– Once a “W” has been reported, don’t repeat it unless it changes . Here, the same plant, concept (height), and units of measurement are discussed throughout.
– Only the date changes , so it and the updated value
( number ) are the only W’s required in the second and subsequent sentences.
The Chicago Guide to Writing about Numbers, 2 nd edition.

• Better: “ The first day after germinating , the plant that was watered daily was 0.7
centimeters (cm) tall . Two days later , it measured 3.8
cm . By two weeks after germination , it had reached 27 cm .”
– The word “it” stands in for “the plant that was watered daily, ” and for references to height , averting repetition of what and “who” (which plant).
– The abbreviation “cm” replaces the full word
“centimeters” after being defined in the first sentence.
The Chicago Guide to Writing about Numbers, 2 nd edition.

• To be able to write correctly and completely about the
W’s and units for the numbers you are working with, you need to read for and take notes on that information.
– In source documents of published numbers.
– In codebooks or questionnaires for data sets.
• Also label
– Units on all variables in your data sets.
• Raw variables (used in the form they came in the original data set).
• Those you calculate.
– W’s and units in all tables and charts you create.
The Chicago Guide to Writing about Numbers, 2 nd edition.

• Mental checklist for reporting one number
– Context (W’s)
– Units
• Same fundamentals apply when
– Comparing two or more numbers or series
• See the podcast by that name
– Reporting results of advanced statistical analyses
• e.g., coefficients from multivariate regression; see Chicago
Guide to Writing about Multivariate Analysis, 2nd Edition.
– Designing effective tables and charts
• See associated podcast
The Chicago Guide to Writing about Numbers, 2 nd edition.

• For basic principles, see chapters 1 and 2 in Miller, J. E.
2015. The Chicago Guide to Writing about Numbers,
2nd Edition.
• For additional examples, see
– Miller, J. E. 2006. “How to Communicate Statistical Findings:
An Expository Writing Approach.” Chance 19 (4): 43–49.
– Miller, J. E. 2010. “Quantitative Literacy across the Curriculum:
Integrating Skills from English Composition, Mathematics, and the Substantive Disciplines.” The Educational Forum 74 (4):
334–46.
The Chicago Guide to Writing about Numbers, 2 nd edition.

• Study guide to The Chicago Guide to Writing about Numbers, 2nd Edition.
– Question #1 for problem set for chapter 4
– Suggested course extensions for
• Chapter 2
– “Reviewing” exercise #1
• Chapter 4
– “Reviewing” exercise #1
– “Applying statistics” exercise #1
The Chicago Guide to Writing about Numbers, 2 nd edition.

Jane E. Miller, PhD jmiller@ifh.rutgers.edu
Online materials available at http://press.uchicago.edu/books/miller/numbers/index.html
The Chicago Guide to Writing about Numbers, 2 nd edition.