JMIR Publications employs professional external copyeditors (see What are the steps during copyediting? and What are the authors' responsibilities during copyediting?) to bring articles into editorial style, so authors do not have to worry too much about the style on initial submission, although it does shorten the production process after acceptance if the article is roughly aligned with our guidelines (see also JMIR's editorial guidelines), and it helps us to find reviewers if the references are properly formatted and have PMIDs.
While pointing out issues in statistical reporting is also a responsibility of the editor/section editor—who should point out missing statistics and incorrectly reported statistics already during the review process (and not rely on external peer-reviewers)—copyeditors act as the "second line of defense" and must enforce reporting in line with generally accepted guidelines. The recent SAMPL Reporting Guideline is a useful resource that should be known and enforced by all copyeditors. For more details on common statistical terms, please refer to the AMA's Glossary of Statistical Terms.
General notes:
- When reporting multiple statistics within parentheses, separate each statistic with a semicolon. For example: (P=.50; OR 2.72, 95% CI 0.45-2.6).
- Do not use possessives for the name of any statistical test (see Use of possessives with eponyms).
Omission of Leading Zero
We follow the guidelines set out by AMA (Section 19.7.1)
AMA states that a zero should be placed before the decimal point for numbers less than 1, except when expressing the 3 values related to probability: P, α, and β. These values cannot equal 1, except when rounding. Because they appear frequently, eliminating the zero can save substantial space in tables and text. (Although other statistical values also may never equal 1, their use is less frequent; to simplify usage, the zero before the decimal point is included.)
Examples:
P=.16
1 − β=.80
Our predetermined α level was .05.
BUT: κ=0.87
Percentages and Decimal Places
- If N < 100, there is no decimal point in the percentage.
- If N is 100 to 999, 1 decimal point is reported.
- If N ≥ 1000, 2 decimal points are preferred, but 1 decimal point is acceptable.
- BUT: If a table contains mixed denominators, be consistent and use, for example, 1 decimal point consistently even if some denominators are less than 100.
- See AMA 2.13.9, 17.3.1, and 17.3.2.
N=87, 45%
N=356, 45.1%
N=1024, 45.13%
Note: Do not use n=488/550, 88.7%; instead, it should be only 488/550 (88.7%).
Percentages Within a Sentence
Preferred JMIR style is to always make clear what the numerators and the denominators are. Of note, do not add a 0 after the decimal if the percentage value is a whole number, (ie, 64/100=64%, not 64.0%). There are no exceptions to this guideline.
In expressing a series of proportions or percentages drawn from the same sample, the denominator need be provided only once.
Of the 200 patients, 6 (3%) died, 18 (9%) experienced an adverse event, and 22 (11%) were lost to follow-up.
Example I:
"the majority of participants (59%) felt that..."
should be revised to
"the majority of participants (59/100, 59%) felt that...." NOT “the majority of participants (59%, 59/100) felt that...."
or if the percentage is used in the sentence,
"…, where 59% (59/100) of the participants felt that…".
Example II:
"a vast majority (n=488, 88.7%) of participants"
should be changed as follows:
"a vast majority (488/550, 88.7%)" (Note: The "n" has been dropped and the "N" value (ie, 550) has been added). When reporting multiple statistics within parentheses, separate each statistic with a semicolon.
Example III:
“a vast majority (488/550, 88.7%; P=.002)”
Do not use square brackets within parentheses for statistics. Separate values with a comma if statistics are linked (ie, % and numerator/denominator); separate values with a semicolon if statistics are unlinked (ie, % and odds ratio).
WRONG:
"The most common functions among studies that involved children with special needs were consultation (8 studies [73%]) and diagnosis (7 studies [64%]). "
Chi-square test
- Include the degrees of freedom (subscript).
- Authors must include the degrees of freedom; if not provided, you will be queried for these values during copyediting.
- Degrees of freedom are subscripted; chi-square symbol is italicized.
- Chi-square value should be reported to only 1 decimal place.
- When reporting chi-square values in a table, include the degrees of freedom in parentheses, eg, chi-square (df).
- The abbreviation for degrees of freedom (df) does not need to be expanded; it should be italicized (AMA glossary of statistical terms 20.1).
Example:
In text: 
In table: Chi-square (df)
Mean, standard deviation, standard error, and range
- Equal signs are not used; separate the value from the statistic with a space.
Examples
mean 4.71 (SD 0.47) cm
range 4-5
SE 2.55
...were aged 20-69 (mean 38.9, SD 11.1) years
When reporting multiple statistics in a sentence, use a semicolon to separate the terms.
Example: “The age (in years) of the participants (mean 4.71, SD 0.47; range 4-5)...”
For mean (SD), we prefer not to use the +/- sign. Instead, an expression like 1.11 ± 2.33 should be formatted as "1.11 (SD 2.33)." Authors are advised to review such changes made by your copyeditor. Copyeditors are advised to add a query notifying the author(s) of this change, in case there are also other statistics that have also been formatted by authors with a +/- sign (eg, SE) and they now need to specify the expression.
When reporting a value that is calculated from a mean and SD value, report it in the following manner: Mean+SD=1.6
Note: When reporting mean and SD in a table, include the mean and SD in the same column with the heading “mean (SD)”.
As of December 4, 2013, AMA no longer requires the expansion of "SD" or "SE" in the text (Section 20.9, page 894 in the print) — See Which abbreviations don't need to be expanded?
Odds ratio and confidence interval
- ORs should always be presented with CIs
- Include 0 before the decimal point
- If one value in the CI range is negative, then “to” should be used rather than a hyphen
OR 1.2 (95% CI 0.9-2.4)
OR 1.2% (95% CI 0.8%-1.6%)
95% CI –0.1 to 0.8
- If any CI range in a table includes a negative number, the word "to" should be used to replace the hyphen in all ranges in that table for consistent presentation within the table.
- Avoid brackets within parentheses. If brackets within parentheses are necessary, use square brackets. We never use parentheses within parentheses. In addition, avoid using parentheses inside another set of parentheses altogether, eg, (OR 2.92 (2.36-3.62)) should be rewritten as (OR 2.92, 95% CI 2.36-3.62).
- CI does not need to be expanded (Section 14.11, page 504 in the print; see Which abbreviations don't need to be expanded? ).
- When defining “OR” within parentheses, use square brackets. Example: (odds ratio [OR] 2.92, 95% CI 2.36-3.62). Note that OR needs to be defined in tables (through a footnote or in the caption).
Confidence limit
Upper and lower boundaries of the confidence interval, expressed with a comma separating the 2 values.
Example: The mean (95% confidence limits) was 30% (28%, 32%).
Interquartile range
- Include 0 before the decimal point.
- Should be formatted as "IQR" followed by a hyphenated range (ie, no equal sign) or when presented alongside a median as "median (IQR)".
Examples:
A median value of 54 (IQR 45-62)...
The median (IQR) was 54 (45-62)...
P value
From our instructions for authors:
- (Again, this is the primary responsibility of the academic editor, but the copyeditor acts as a second line of defense if this has been overlooked by the editor/section editor)
- Note for copyeditor: point author to the relevant section in the Instructions for Authors, if P values are missing (ie, "no significant differences were found..." without stating the P level), incorrectly reported, or replaced by statements of inequality (or in Tables * / ** footnotes) such as P<.05.
- The actual P value should be expressed rather than a statement of inequality (P=...), unless P<.001 or P=.99 or P=0 (which should be changed to P<.001) or P=1 (which should be changed to P>.99). In other words, for expressions like P<.05, authors will be queried to provide the actual P value during copyediting.
- P values cannot be 0 or 1—change to <.001 or >.99, respectively. Note for copyeditor: add a comment to the manuscript in copyediting saying something like “Because P values theoretically cannot reach 1, AMA Manual of Style guidelines are that the highest P value to report is ‘P=.99’ so I have changed them accordingly” (and similar for P=0).
- P values less than .001 (including 0.000) are not allowed and are to be converted to the expression P<.001. In other words, for example, P<.0001 or P=.0005 must be rewritten as P<.001.
- P is italicized and capitalized (Note: Our typesetting scripts are actually intelligent enough to convert the P to italics if the copyeditor forgets this).
- DO NOT use zero before the decimal point.
- The actual value of P should be expressed to two digits, whether or not it is significant.
- If P<.01, P should be expressed to three digits.
- When rounding, 3 digits are acceptable if rounding would change the significance of a value (eg, P=.049 rounded to .05).
- No spaces in expressions with mathematical operators. Remove these spaces to adhere to our preferred format without blanks. The same is true for other equality and inequality expressions (eg, P < .001 should be changed to P<.001 and n = 12 should be corrected to n=12).
- In a table, the column heading should be “P value” not “P”. Note that "value" should not be italicized.
- All footnote symbols within a table are superscripted letters (a-z). The use of *, **, *** footnotes to mark significance levels (eg, P<.05, P<.01, P<.001) is discouraged. Authors are asked to provide exact P values instead. While we prefer the exact P values, there are exceptions to this general rule. The use of *, **, *** footnotes to indicate significance levels is allowed in the following instances:
- In tables of systematic reviews, which tend to be busy and where the original P values can't be found in the original publications
- When Odds Ratios instead of P values are presented
- If for any reason authors are unable to provide the exact P values
Examples:
P=.60
P=.37
P=.02
P=.008
P=.049
P<.001
NOTE for P values for very large sample sizes (according to AMA guidelines)
Excerpt from AMA: “Though our style manual recommends (Section 20.9, page 888 in the print) that "[expressing] P to more than 3 significant digits does not add useful information to P<.001," in certain types of studies (particularly GWAS [genome-wide association studies] and other studies in which there are adjustments for multiple comparisons, such as Bonferroni correction, and the definition of level of significance is substantially less than P<.05) it may be important to express P values to more significant digits. For example, if the threshold of significance is P<.0004, then by definition the P value must be expressed to at least 4 digits to indicate whether a result is statistically significant. GWAS express P values to very small numbers, using scientific notation. If a manuscript you are editing defines statistical significance as a P value substantially less than .05, possibly even using scientific notation to express P values to very small numbers, it is best to retain the values as the author presents them.”
If a study has a very large sample size, it may be necessary to report P values to a value smaller than P<.001 in order to show statistical significance. This will be up to editorial discretion.
N and n
- N designates the entire population under study.
- n designates a sample of the population under study.
- Do not insert spaces before and after the sign, and delete spaces on either sides of mathematical operators, except in equations.
Examples:
N=468
n=234
F test
- Degrees of freedom are subscripted in the text.
- In a table, degrees of freedom are included in parentheses after the number; ie, “F test (df).”
Example:
t test
- t is italicized.
- Include the degrees of freedom (subscript).
- Include 0 before the decimal point.
- Authors must include whether the test is 1-tailed or 2-tailed.
- Authors must include the degrees of freedom; if not provided, you will be queried for these values during copyediting.
- In a table, degrees of freedom are included in parentheses after the number; ie, “t test (df).”
Example:
Effect size
- Include 0 before the decimal point.
...an effect size of 0.277 standard deviation units.
Cronbach alpha
- DO NOT use “Cronbach’s” alpha.
- There is no zero before the decimal point.
Example:
Cronbach α=.78
Cohen d
- DO NOT use “Cohen’s” d with the possessive
- Include a zero before the decimal point if the value is less than 1.
Example:
Cohen d=0.29
Cohen d=1.45
Beta level
- There is no zero before the decimal point.
Example:
β=.2
Spearman rank correlation
- The symbol is ρ (rho).
- Include a zero before the decimal point if the value is less than 1.
Example:
ρ=0.67
Pearson correlation coefficient
- The symbol is an italicized r.
- Include a zero before the decimal point.
Example:
r=0.92
Kappa statistic
- The symbol is κ (kappa).
- Include a zero before the decimal point if the value is less than 1.
Example:
κ=0.50
The κ value indicating interobserver reliability was 0.5.
Equal and “inequality” signs
- DO NOT insert spaces before and after the sign.
- Remove blank spaces on either sides of mathematical operators to adhere to our preferred format without blanks. The same is true for other equality and inequality expressions, eg, (P < .001) should be changed to (P<.001) and (n = 12) should be corrected to (n=12).
- For greater than or equal to and less than or equal to signs, insert a single symbol using MS Word (Mac shortcuts ≥: option+ ; ≤: option+<; Windows shortcuts ≥: ALT+8805 ; ≤: ALT+8804)
- DO NOT use an underlined greater than/less than symbol.
Examples:
x=15
n2
y≤0
Greek letters in text
- Greek letters are used as per the AMA guidelines: Use of Greek letters rather than spelled-out words is preferred, unless common usage dictates otherwise (eg, tau protein).
- In titles, subtitles, headings, and at the beginning of sentences, the first non-Greek letter after a lowercase Greek letter should be capitalized.
Examples:
Cronbach α
Beta-thalassemia
β-Blockers help control heart rate...
Currency
- Specify all currencies in US$. For amounts reported in non-US currency, the current exchange rate should be used to calculate the amount in US dollars, and that amount should be shown in parentheses. For example, "Each participant was rewarded with Amazon gift cards worth CAD $5 (US $7.18) for their participation"
- If there are more than 10 instances of another currency presented, a blanket statement of the exchange rate from the currency they have mentioned to US$ should be included. For example, "A currency exchange rate of CAD $1=US $0.72 is applicable." This rate should be the current conversion rate and is available online here: https://www1.oanda.com/currency/converter/ (AMA-recommended resource). You can directly add this into the manuscript (and ask the author to verify) or ask the author to add it in for you.
- For all currency measures, refer to the 11th edition of the AMA here: https://www.amamanualofstyle.com/view/10.1093/jama/9780190246556.001.0001/med-9780190246556-chapter-17-div2-34?rskey=z4zEI1&result=1
- DO NOT use zeros after whole numbers of currency.
US $99
CAD $125.35
€40
Aus $100 (Note: AMA says "A$" for Australian dollars, but since we use a space before the $, this would be confusing as "A $100"; therefore, we'll abbreviate to "Aus $")
Complex equations
In text, whenever possible, equations should be inserted using characters from the Symbols list of MS Word. Equations can be inserted within a paragraph (run-in with the text) or on a separate line. Do NOT use the equation editor/tools in Word. The special formatting will not be picked up by our scripts.
Simple equations that are kept in text should be indented and numbered (number in bold) in parenthesis after the equation itself if they meet the following criteria: (1) If there are numerous equations (3 or more) in a manuscript, (2) if the equations are related to each other, or (3) if the equations are referred to after initial presentation.
Example:
yi = Ci - ci (1)
Use spaces between all mathematical operators in complex equations (including “=”). Note in this case, “=” is functioning as an operator, it is not a statement of equality. In the case of “n=2,” no spaces are used as it is a statement of equality.
"Trending" towards significance
We do not use "trending towards significance" or other variants.
For example, "There was a trend (P=.06) showing that...was significant".
It's fair to say that there was a trend in something, but this must be followed up with "...but these results were not statistically significant."
Alternatively, it's best to simply state the results' significance and not use variations of "trend".