Numbers in your thesis: Should you use words or numerals?

Even experienced writers find it tricky to decide how to handle numbers within the body of their thesis. To make matters worse, many style guides use very different formats. What is a student to do?

This article provides tips that will help you handle this issue within your writing. These tips are based on the APA guidelines related to numbers.

The basic rules

Numbers can be written either as words (e.g., one hundred) or numerals (e.g., 100). The basic rule is to use words for numbers from zero through nine, and then numbers from 10 onwards. This is true for both cardinal numbers (e.g., two, 11) and ordinal numbers (e.g., second, 11^th). However, there are some exceptions:

• Use numerals for numbers from zero to nine that are followed by a precise unit of measurement or grouped together with a number that is ≥ 10.

Examples:

The samples measured 7 cm in diameter. (“cm” is a unit of measurement)

However, only 3 of the 12 were usable. (“3” is being grouped with “12”)

But: These three samples were subjected to further testing.

• Use words for any number that is used to start a sentence, with the exception of years.

Examples:

Seventy-two thousand ink cartridges are sold every day.

Nineteenth-century novels often feature complicated plot lines.

But: 2008 saw record olive crops throughout the Mediterranean.

• Use words for common fractions and set expressions.

Examples:

According to the survey, one half of the employees are dissatisfied.

Understanding the Five Pillars of Islam is a critical first step.

The Fourth of July is traditionally marked by a firework display.

Writing percentages

With percentages, the standard is to use numerals and “%” (not “percent”).

Example:

According to the report, 45% of the workforce is employed in the service sector. Only 6% currently work in agriculture.

The main exception is if you are using a percentage to begin a sentence. In this case, use words to express the entire percentage.

Example:

Thirteen percent of the patients reported that their symptoms improved after taking the experimental drug.

Reporting results that include numbers

If your thesis includes quantitative research, you probably have data to report. Statistics, mathematical functions, ratios, and percentages are all written using numerals. This is true regardless if they are included within a table or as part of the actual text. Keep the following guidelines in mind:

• Report most statistics to two decimal places (such as M = 5.44).
• Report statistics that could never exceed 1.0 to three decimal places (such as p < .001).
• Report percentages and degrees of freedom as whole numbers (such as 73%).
• Italicize values that are not Greek letters (such as M, SD, p, and F).
• Include spaces before and after =, >, and <.

Examples:

The average IQ of the participants was relatively high (M = 137.33, SD = 4.54).

The results of the second test were statistically significant, t(12) = 4.11, p < .05.

Writing numbers that are accompanied by measurements

If a number comes immediately before a unit of measurement, use numerals.

Examples:

Each patient received a 5-mg dosage of the experimental drug.

The tallest participant was 2.03 m.

Also use numerals for precise ages, times, dates, scores, points on a scale, and amounts of money.

Examples:

The final score of Ghana 2, Brazil 1 did not represent a decisive victory.

Children under 8 years receive a $50 discount.

But: Most girls start reading when they are about five years old. (“about” makes the number imprecise)

Writing long numbers

Longer numbers follow specific rules:

• Use a period to indicate a decimal point.
• Starting with 1,000, use commas to separate every three digits.
• Starting with a million, use a combination of numerals and words.

Examples:

The region has an average of 43.75 doctors for every 10,000 people.

Some predict that the number of users will reach 2 billion by 2020.

Consistency may not be obvious

One of the main reasons why writing numbers is complicated is that consistently applying the rules may lead to a text that actually seems very inconsistent. Consider the following paragraphs:

Examples:

At about the age of seven, the girl’s height was 1.47 m. This placed her in the fifth percentile, although her weight placed her in the top 7% of her class. By the time she was 9 years old, she was taller than halfof the boys in her year. Five years later, she was still ranked 15th.

Thirteen thousand viewers watched the performance of Shakespeare’s Twelfth Night from the park, while another 2,000 watched from the surrounding buildings and 1.2 million watched it on television. As 1 out of every 11 residents saw at least part of the play, this one event can definitely be considered a success.

These texts may look awkward because so many different number formats have been used, but don’t be deceived – the above guidelines have all been followed.

If you are not required to strictly follow a particular style (such as APA), you may have some flexibility to modify the guidelines presented in this article. Just be sure to apply any modifications you make throughout your entire document.