Answered By: Katie Hutchison Last Updated: Sep 01, 2016 Views: 28834
Here is what APA describes for numbers:
Use numerals to express:
a. numbers 10 and above
examples: 12 years old, the 57th trial, 12 cm wide
b. numbers that precede a unit of measurement
examples: 5-mg dose, 36.3 mm
c. numbers that represent statistical or mathematical functions, fractional or decimal quantities, percentages, and ratios
examples: multiplied by 5, .33 of the..., more than 5% of the sample..., a ratio of 15:1
d. numbers that represent time, dates, ages, scores, points on a scale, exact sums of money and numerals
examples: 1 hr 34 min., at 3:45 am, 2-year olds, score 5 on a 12 point scale
Use numbers expressed as words:
a. when the number begins a sentence, title, or heading
examples: Forty-eight percent of the sample..., Twelve students improved...
b. common fractions
examples: one fifth of the class..., two-thirds majority
c. universally accepted language
examples: the Twelve Apostles, Five Pillars of Islam
As for percentages specifically, APA has this to say:
1. Use the percent symbol after any number expressed as a numeral. For example: 12%. In APA style, numbers greater than nine are expressed as numerals and use the percent symbol.
2. Use the word "percent" after any number expressed as a word. For example: five percent.
3. Use the word "percent" after any number that begins a sentence, title or text heading. The APA rule for numbers is that you should begin a sentence with a word even if the number is greater than nine, and the word "percent" should also be used. For example: Forty-eight percent of the sample showed an increase.
4. Use the percent symbol in tables and figures even if the symbol follows a number smaller than 10; APA style directs writers to use symbols in those cases to save space.
5. Use the word "percentage" when you do not provide an exact number. For example: The student determined the percentage of rats that ate the food in the control condition.
For more information, see the Publication Manual of the American Psychological Association.