The number one mistake students make when writing in APA style is presenting numbers incorrectly. Sometimes it seems that you should write a number out in word form, but this is usually not the case in APA style. APA style is the formatting and citation style used and recommended by the American Psychological Association. As such, it's usually employed for writing about scientific endeavors in which exact numerical figures are key.
Writing About Numbers in APA Style
When writing in APA style, write numbers out in words for sums below 10. For sums above 10, write the number in numeral form.
Example: Nine of the students in class write with pencils, but 12 students prefer to write in pen.
Numbers are also written in numeral form if they represent dates or times.
Example: She broke her ankle 3 years ago.
Use numbers when referring to a specific place in a book as well.
Example: See Column 1 in Table 5 for more information.
When to Write Out Numbers
In some instances, you'll need to write out numbers in word form. Write numbers out when they refer to measurements below 10 that don’t require precision or when the number begins a sentence, heading or title.
Writing About Money in APA Style
In most cases, writing about money in APA style means writing about exact sums. Use the symbol for the currency you’re writing about.
Example: My mother gave me $5 to buy a snack.
Use numerals to indicate cents after the decimal point.
Example: A ticket to the movies costs $7.50 with a student ID.
When writing about sums of money with exact change, place the cent amount behind the decimal point. Don't begin with a zero if there's not a full dollar amount. It's also permissible to omit the dollar sign in these cases.
Example: After I bought lunch, the cashier gave me .23 cents in change.
For large sums of money, you can write out part of the amount if an exact number isn't needed.
Example: The country budgeted $4 trillion dollars for those services.
Use a decimal point to indicate a fraction of a large sum.
Example: The CEO paid himself $5.6 million dollars last year.
However, if you need to write out an exact sum, use numerals only.
Example: The company’s profit margin was $1,334,267 dollars last year.
Writing About Foreign Currencies
When writing about foreign currencies, the same rules apply. Change the currency symbol when necessary, and write out the type of currency if that's unclear. Use currency abbreviations, such as AUD for Australian Dollars, for clarity.
Example: When I landed in London, I exchanged my money for £100 at the airport.
Example: The exchange rate for Brazilian Reals is R$3.76 for one U.S. dollar.
Remember that clarity is key. Sometimes you may be tempted to break these rules in the name of clarity. However, if your writing is unclear, that should indicate the need to rearrange your sentence rather than break a rule.