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Academic Coaching & Writing

II. Using APA Style in Academic Writing: Words or Numerals?

Dec 22, 2014 by Jeff Hume-Pratuch

What’s the number one problem area for writers in APA Style? Numbers! Whether it’s spelling them out or writing them as numerals, numbers are a common source of errors in research papers. This is surprising in a way, because the basic approach to numbers in APA Style is very simple:

  • Use words for numbers from one to nine.
  • Use numerals for numbers 10 and up.

If these were the only rules to remember, APA Style would be a breeze: Number of things counted ≥ number of toes = numerals! Like most rules, however, these have a few quirks. Let’s look at them one by one.

Always use words for

  • numbers that begin a sentence, title, or heading. (This can be clumsy for large numbers; avoid the problem by reworking the sentence, if possible.)
  • simple fractions (i.e., those in which both parts are whole numbers).
    • one half of the participants
    • a three-fifths majority
  • “universally accepted usage” for certain proper nouns. (Unfortunately, there is no APA-approved list of terms to which this rule applies. The best advice is to use the terminology generally accepted in your field of study.)
    • the Twelve Apostles
    • the Twelfth Imam 

Always use numerals for

  • numbers in the abstract of your paper. (Why? Because brevity is the soul of the abstract, and numerals take up less space than words. This was crucial at the beginning of the Internet era, when the abstract field in online databases was the length of a couple of tweets.) Keep in mind, however, that the word one can be a pronoun as well as a number, and pronouns are never represented by numerals.
    • Correct: This paper reviews the results of 8 studies of somatic signaling.
    • Correct: Participants evaluated one another’s maze performance.
    • Incorrect: Participants evaluated 1 another’s maze performance.
  • any number followed by a unit of measurement.
    • 2 cm
    • 500 mg of acetaminophen
    • 98.6 °F
    • 2 hr 15 min
    • 25 €
    • 15-year-old Scotch
  • expressions of statistical or mathematical functions, decimal fractions, proportions, percentages, and so forth.
    • divided by 3
    • 5 times as many
    • a ratio of 5:1
    • the 97th percentile
    • 1.3% of the sample
  • numbers that represent scores, points on a scale, numerals as numerals, and any numbers in a figure or graph.
    • a score of 5 on a 7-point Likert-type scale
    • a stimulus displaying the number 2 in red
  • numbers indicating a specific point in a numbered series, and each number in a list of four or more numbers.
    • Chapter 4
    • Study 1
    • Correct: At Time 2, the four doses had been eaten by 4, 7, 9, and 15 rats, respectively.
    • Incorrect: At Time 2, the four doses had been eaten by four, seven, nine, and 15 rats, respectively.

A Puzzling Exception

“Use words for approximations of numbers of days, months, and years (e.g., about three months ago” (APA Publication Manual, 4.31e, p. 112). The manual is silent about approximations of weeks, decades, or centuries. In the absence of specific instructions, use your own judgment to format approximations of other lengths of time.

Numerals and Words Together

Sometimes two numbers wind up back to back as modifiers of a noun. This can get ugly: “10 7-point scales” is easy to misread as “107-point scales,” which would play havoc with anyone trying to replicate your data. Instead, APA Style increases readability by using a combination of words and numbers to express back-to-back numbers.

  • ten 7-point scales   
  • 3 two-way interactions
  • twenty 6-year-olds

How do you tell which of the two numbers should be the numeral, and which should be the word? Look at the base expression: 7-point scales, two-way interactions, 6-year-olds. For the number in the base expression, follow the usual format (word or numeral); then add the second number in the other format.

In the next blog in this series, you’ll learn about common problems writers have with commas. Meanwhile, let us know what aspect of APA Style you struggle with. We’ll try to address your concerns in future blogs.

  • Laura Cherry says:

    Dec 11, 2017 at 8:52 am

    How do you handle it when these rules conflict? For instance, do you use a numeral when the number is a math expression, but it begins a sentence? Ex. "Three times a number, n, minus four, is equal to fifteen." Laura, "Use words to express any number that begins a sentence, title, or text heading. (Whenever possible, reword the sentence to avoid beginning with a number.)" APA Publication Manual, 6th ed., 4.32

  • Lady Ruth Smith says:

    Jun 28, 2018 at 10:53 pm

    How do you handle it when these rules conflict? For instance, do you use a numeral when the number is a math expression, but it begins a sentence? Ex. "Three times a number, n, minus four, is equal to fifteen." Laura

  • ACW says:

    Jul 02, 2018 at 12:58 pm

    Use words to express any number that begins a sentence (e.g., "Three" in the example). Use numerals for numbers that represent mathematical functions (e.g., 4, 15). The correct format would be: "Three times a number, n, minus 4, equals 15." It would also be correct (and possibly preferable) to express this as an equation in the line of text: (3 x n) - 4 = 15. Hope this helps, Jeff

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