19.6 Abbreviating Number
The word number may be abbreviated No. in the body of tables and line art or in the text when used as a specific designator. Do not use the number sign (#) in place of the abbreviation. The word number should always be spelled out when it is used as a proper noun (eg, “Social Security number”).
No. of participants
A No. 10 catheter was placed in the femoral artery.
When referring to numbers of individuals in a study—in tables, figures, and within parentheses—the abbreviation N is used when referring to the entire sample; n refers to a subsample. (See also 20.9, Study Design and Statistics, Glossary of Statistical Terms.)
Patients were enrolled at each study site (N = 2758) and randomly assigned to intervention (n = 1378) or placebo (n=1380).