Formal tables in scientific articles conventionally contain 5 major elements: title, column headings, stubs (row headings), body (data field) consisting of individual cells (data points), and footnotes (Example T1). Details pertaining to elements of style for table construction vary among publications; what follows is based on the general style of JAMA and the Archives Journals.
Each table should have a brief, specific, descriptive title, usually written as a phrase rather than as a sentence, that distinguishes the table from other data displays in the article. The title should convey the topic of the table succinctly but should not provide detailed background information or summarize or interpret the results.
Tables should be numbered consecutively according to the order in which they are mentioned in the text. The word “Table” and the table number are part of the title.
If the article contains only 1 table, it is referred to in the text as “Table.” The capitalization style used in article titles should be followed for table titles (see 3.9, References, Titles). The following are examples of table titles:
Table 1. Symptoms and Signs of Chronic Fatigue Syndrome
Table. Relationship of Blood Pressure and Intraocular Pressure in Patients With Open-Angle Glaucoma
The main categories of information in the table should have separate columns. In tables for studies that have independent and dependent variables, the independent variables conventionally are displayed in the left-hand column (stub) and the dependent variables in the columns to the right. Each column should have a brief heading that identifies and applies to all items listed in that column. The stub, however, may not require a heading, particularly if the elements in the stubs are very different. If relevant, the unit of measure should be indicated in the column heading (unless it is given in the table stub) and is preceded by a comma. Column headings are set in boldface type. If necessary, column subheadings may be used. For more complex headings, braces may be used (Example T4) or additional explanatory information may be provided in the footnotes.
If all elements in a column are identical (eg, if all patients were women and a column indicated the patients' sex), this information could be provided in a footnote or in the table title and the column deleted.
In column headings, style guidelines regarding numbers (eg, use of ordinals) and abbreviations may be relaxed somewhat to save space, with abbreviations expanded in a footnote. However, when space allows spelled-out headings, expansions are preferable to abbreviations. The capitalization style used in titles should be followed (see 3.9, References, Titles).
Table Stubs (Row Headings).
The left-most column of a table contains the table stubs (or row headings), which are used to label the rows of the table and apply to all items in that row. If a unit of measure is not included in the column heading, it should be included in the stub. Stubs are capitalized according to style for sentences, not titles. Therefore, if a symbol (such as %), an arabic numeral, or a lowercase Greek letter (such as β) begins the entry, the first word to follow should be capitalized. Stubs are left-justified, and indentions are used to depict hierarchical components of the stubs (Example T5). However, some publications use bold stubs or shading instead.
For a table that may be readily divided into parts to enhance clarity or for 2 closely related tables that would be better combined, cut-in headings may be considered.1 The cut-in heading is placed above the table columns (below the column heads) and applies to all tabular material below. Cut-in headings are set boldface, are centered, and have a rule above (but not below) them (Example T6). However, cut-in headings may interfere with downward scanning and thus should be used with care.2
Both column headings and stubs should be consistent in style and presentation between tables in the same article.
The field or body of the table presents the data. Each data entry point is contained in a cell, which is the intersection of a column and a row. Table cells may contain numerals, text, symbols, or a combination of these. Data in the field should be arranged logically so the reader can find an individual data point in the table easily. For instance, time order should be used for data collected in sequence (Example T4). Similar types of data should be grouped. Numbers that are added or averaged should be placed in the same column. Text in the field cells should be capitalized in sentence style (ie, the first word is capitalized and all that follow in the cell are lowercased).
Missing data and blank space in the table field (ie, an empty cell) may create ambiguity and should be avoided, unless an entry in a cell does not apply (eg, a column head does not apply to one of the stub items).1 The numeral 0 should be used to indicate that the value of the data in the cell is zero. An ellipsis (…) may be used to indicate that no data are available for a cell or that the category of data is not applicable for a cell. However, ellipses should not be used to denote different types of missing elements in the same table. Other designations such as NA (for “not available,” “not analyzed,” or “not applicable”) may be used, provided their meaning is explained in a footnote (Example T7).
Blank cells may be acceptable when an entire section of the table does not contain data (Example T8).
Totals and percentages in tables should correspond to values presented in the text and abstract and should be verified for accuracy. Any discrepancies (eg, because of rounding) should be explained in a footnote.
Boldface type for true totals (ie, those that represent sums of values in the table) should be used with discretion. Boldface should not be used to overemphasize data in the table (eg, significant odds ratios or P values).
Alignment of Data.
Horizontal alignment (across rows) must be considered in setting tables. If the table stubs contain lines of text that exceed the width of the stub column (runover lines in the table stub) and the cell entries in that row do not, the field entries should be aligned across the first or top line of the table stub entry (Example T9). This top-line alignment of data applies to tables that have numbers, words, or both as cell entries. If some entries within the table field contain information that cannot be contained on a single line in the cell (runover lines in the table field), the table entries in that row also should be aligned across on the first line of the stub entry.
Vertical alignment within each column of a table is important for the visual presentation of data. Whenever possible, columns of data should be aligned on common elements, such as decimal points, plus or minus signs, hyphens (used in ranges), virgules, or parentheses (Example T8). If table entries consist of lengthy text, the flush-left format should be used with an indent for runover lines. If entries in a column are mixed (ie, if no common element exists or if the numbers vary greatly in magnitude), primary consideration should be given to the visual aspects of the entire table and the type of material being presented.
Rules and Shading.
For JAMA and the Archives Journals, tables should be submitted without rules drawn in (as opposed to table borders, which are appropriate) or shading. If these elements are included they will have to be manually removed during the editing process (see 4.1.9, Guidelines for Preparing and Submitting Tables).
Many journals add rules and shading during the production process. For example, JAMA uses horizontal rules to separate rows of data (Example T8). Other journals use shading for the same purpose.
Footnotes may contain information about the entire table, portions of the table (eg, a column), or a discrete table entry. The order of the footnotes is determined by the placement in the table of the item to which the footnote refers. The letter for a footnote that applies to the entire table (eg, one that explains the method used to gather the data or format of data presentation) should be placed after the table title (Example T4). A footnote that applies to 1 or 2 columns or rows should be placed after the column heading(s) or stub(s) to which it refers (Example T7). A footnote that applies to a single entry in the table or to several individual entries should be placed at the end of each entry to which it applies (Example T10).
For both tables and figures, footnotes are indicated with superscript lowercase letters in alphabetical order (a-z). The font size of the footnote letters should be large enough to see clearly without appearing to be part of the actual data. While some publications (including, formerly, JAMA and the Archives Journals) use symbols (*, †, etc) to indicate footnotes in tables, such symbols are ordered arbitrarily and are limited in number. Use of superscript letters ensures a logical order to the entries and a much larger supply of notations (26 characters). For tables in which superscript numbers and/or letters are used to display data, care should be taken to ensure that superscript footnote letters are distinguished clearly from superscripts used for data elements (for example, see Table 15.1.2, Nomenclature, Blood Groups, Platelet Antigens, and Granulocyte Antigens, Platelet-Specific Antigens). In these situations, use of the symbol footnotes may help avoid confusion.
Footnotes are listed at the bottom of the table, each on its own line. However, to save space, tables with more than a few footnotes can run them in 2 columns (Example T10).
Footnotes may be phrases or complete sentences and should end with a period. Any operational signs, such as <,>, or =, imply a verb. For example, P = .01 is considered a complete sentence (“P is equal to .01.”) when used as a table footnote. Footnote letters should appear before the footnote text and are followed by a space for clarity. In JAMA and the Archives Journals, the abbreviations and units of measure conversion footnotes appear first and are set off with an introductory word or phrase instead of a letter. In addition, abbreviations are expanded in alphabetical order; units of measure and applicable conversion factors are listed in a separate footnote (Example T11).
If several tables share a detailed or long footnote that explains several abbreviations or methods, this footnote may appear in the first table for which it is applicable, and a footnote in each succeeding table for which the footnote also is applicable may refer the reader to the first appearance of the detailed information:
Study acronyms are explained in the first footnote to Table 1.
The reader also may be referred to a relevant discussion in the text by a footnote:
See the “Statistical Analysis” section for a description of this procedure.
Several of the most common uses of footnotes include the following.
To expand abbreviations:
Abbreviations: CI, confidence interval; OR, odds ratio.
a Scores are based on a scale of 1 to 10, with 1 indicating least severe and 10, most severe.
To provide information on statistical analyses or experimental methods:
b Adjusted for age, smoking status, and body mass index.
To explain a discrepancy in numerical data:
a Because of rounding, percentages may not total 100.
To cite references for information used in the table. References are given as in the text and are designated with superscript arabic numbers:
c Classified using International Classification of Health Problems in Primary Care.45
a Data from the US Census Bureau.5
To acknowledge credit for reproduction of a table. If the table has been reprinted or modified with permission from another source, credit should be given in a footnote:
a Adapted with permission from the American Medical Association.41
References for information in a table or figure should be numbered and listed as if this information were part of the text. For instance, if the source from which the material referred to in the table or figure is one of the references used in the text, that reference number should be used in the table or figure. If the reference pertains only to the table or figure (ie, the source is not cited elsewhere in the text), the reference should be listed and numbered according to the first mention of the table or figure in the text (see 3.6, References, Citation). All references in an article should appear in the reference list.
Note that references cited at the end of table titles are ambiguous. Instead, a footnote should be added with an explanation that it was
Adapted from …
Reproduced with permission from …
Data were derived from …
When both a footnote letter and reference number follow data in a table, set the reference number first followed by a comma and the letter (see also 3.6, References, Citation).