Q: I appreciate the difference between percentile and percentage, but can you shed light on the difference between percentile and centile?
A: Ed Livingston, MD, a JAMA deputy editor and author of the statistics chapter in the 11th edition of our style manual, responds:
Percentile refers to the percentage below which a group of observations fall, ie, 93 percentile means that 93% of the observations fell below that value. If I had a score that was in the 85th percentile, I had a score that was better than 85% of all people taking that test.
Centile refers to which group an observation belongs to when the population is divided into 100 equal groups, like a quartile. With a quartile there are 4 equal-sized groups and with a centile there are 100 equal-sized groups—so in practice it’s the same as a percentile. —Cheryl Iverson, MA
Q: How should a photograph or illustration be cited in the reference list?
A: In the reference list, cite the article in which the figure you want to reference appears in the “usual” way of citing a journal article. In the text, where you cite the reference, use the following style:
As Christiansen and Fischer [add superscript citation here to the appropriate reference number…you could also include the number of the page on which the figure you are citing appears, in parentheses] illustrate in Figure 1 of their study….
—Cheryl Iverson, MA
[Editor’s Note: I love the idea of referencing a sound!]
Q: How should a “free sound” from the website Freesound.org be cited in the reference list?
A: We would recommend the following for citation format, altering the accessed date to reflect the date it was accessed:
Crickets. http://freesound.org/people/rfhache/sounds/52755/. Posted May 2, 2008. Accessed February 1, 2016.
We are revising our manual now for the 11th edition and will be including many more examples of electronic references.—Cheryl Iverson, MA
Q: Should “least squares mean” be hyphenated? Can the acronym LSM be used or is LS preferred?
A: In the glossary in the statistics chapter, you’ll see that there is no hyphen used in “least squares method,” so I would extrapolate from that to say no hyphen is required in “least squares mean.” If this term comes up so frequently in the manuscript that you feel an abbreviation is warranted, we indicate no preference for what that abbreviation is. Just be sure it’s used consistently throughout.—Cheryl Iverson, MA
Q: If I have a title with a colon, is the first word after the colon capitalized or lowercased?
A: If you are speaking about title and subtitle on the manuscript itself, every major word in the title and subtitle, as well as the first word of title and subtitle, would begin with a capital letter.
Endless and Essential: The Tug-of-War Over Off-Label Use
If you are speaking about the title and subtitle of a journal article as it appears in the reference list, only the first word of the title and any proper nouns would begin with a capital letter.
19. Incollingo J. Endless and essential: the tug-of-war over off-label use. Cataract & Refractive Surgery Today. 2016;16(5):19-27.
More about capitalization of titles can be found in chapter 10.—Cheryl Iverson, MA
Q: Is it necessary to repeat the manufacturer name, city, and country after every repeated mention of a product, or is it sufficient to cite this information only after the first appearance?
A: Mention of the manufacturer’s name after the first mention should be sufficient. Also, please look at our (free) online Updates.
UPDATE: Manufacturer information for Equipment, Devices, and Reagents: In section 15.5 (page 583 in the print book), we will no longer require the inclusion of the location of the manufacturer. This is so easy to look up online, should anyone desire more specific details, that we believe it is not necessary to continue to require this. This change was made October 4, 2011.
You’ll see that we no longer require the manufacturer’s location to be included.—Cheryl Iverson, MA
Q: A colleague is adamant about citing page numbers even if the reference is used more than once in a paragraph. Is this necessary?
A: There is a little advice on citing page numbers in the manual, just above section 3.7.
If the author wishes to cite different page numbers from a single reference source at different places in the text, the page numbers are included in the superscript citation and the source appears only once in the list of references. Note that the superscript may include more than 1 page number, citation of more than 1 reference, or both, and that all spaces are closed up.
Example: These pages showed no sign of proactive sphincteric adduction.3(p21),9
You’ll notice that it’s not mandatory and our style includes, “If the author wishes.” Page number citation can be helpful to the diligent reader who wants to go to the source cited and find the exact mention of the quoted material.—Cheryl Iverson, MA
Q: Is it correct to leave “post” as a separate word in the following sentence? “These activities must take place from prelaunch to post launch.”
A: In section 8.3.1 (“When Not to Use Hyphens”), you’ll see the following:
Note that when post is used as a combining adjectival form, as in postmortem examination, it is set closed up. When it is used as an adverb, as in post hoc testing, it is set as 2 separate words.
So in your example, you would not close up “post launch.” However, the meaning of this sentence is ambiguous to me. I would suggest rephrasing it to avoid an awkward construction and to clarify exactly what interval you are talking about. How about “These activities must take place both before and after launch.”?—Cheryl Iverson, MA
Q: What guidance can you offer as to the inclusion of white space in a publication? My company prefers that level 1 headings begin on a new page, but if the text beneath the heading is only a single paragraph, wouldn’t it be preferable for that heading and its text to share the page with the preceding or the subsequent heading and text?
A: This is really an individual decision for each publisher/publication. Especially in the days of print-only publications, many journal editors tried to optimize the use of every page as each journal had a page budget per issue/per year. In some of the JAMA Network specialty journals. for instance, the journal editors specifically developed short items that could be placed, as space allowed, at the ends of articles that ended with at least half a page of white space…thereby using every bit of space that they could to provide interesting and educational information to their readers. White space was never (to my knowledge) used within an article in the way you are describing.
In the JAMA Network journals, there is no page break before the major headings in an article (eg, Methods, Results, Discussion). This would indeed create a lot of white space. In books, on the other hand, this is fairly customary…you do see that each chapter begins on a new page.
In conclusion, to start each major part of a journal article on a new page would create a very odd-looking journal with lots of white space scattered willy-nilly throughout. Perhaps the desire to emphasize each major part of an article could be accomplished with some other design consideration (eg, style of headings).—Cheryl Iverson, MA
Q: I would like to know how to reference a Kindle book.
A: This question was addressed on this very blog on May 7, 2012. We love questions, though, so feel free to send them in as well as using the search box on the top right corner of the blog home page. Also, we are working now on revising the manual for the next edition and we will be including lots more examples of online reference styles.
Q: How should an “e-pub ahead of print” reference be cited in the reference list?
A: There are a few examples in the current manual, but we plan to include many more examples of citing electronic documents in the next edition—and we are deep in discussions (some might say “arguments”) about a style change, so stay tuned! See 3.15.1, examples 14 through 17. Note, however, that we have now dropped the words “ahead of print” in the phrase that appears in brackets. Here is an example from JAMA Pediatrics:
Keren R, Shah SS, Srivastava R, et al. Comparative effectiveness of intravenous vs oral antibiotics for postdischarge treatment of acute osteomyelitis in children [published online December 15, 2014]. JAMA Pediatr. doi:10.1001/jamapediatrics.2014.2822.
Q: How would I introduce an abbreviation that first appears in a compound word? For example, if my first use of traumatic brain injury was in TBI-related complications?
A: I would recommend the following: traumatic brain injury (TBI)–related injuries. (That’s an en-dash before related.)—Cheryl Iverson, MA