How Long Should the Methods Section Be? Data from 61,514 Examples

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I analyzed a random sample of 61,514 full-text research papers, uploaded to PubMed Central between the years 2016 and 2021, in order to answer the questions:

What is the typical length of a methods section? and which factors influence it?

I used the BioC API to download the data (see the References section below).

Here’s a summary of the key findings

1. The median methods section was 1,126 words long (equivalent to 45 sentences, or 10 paragraphs), and 90% of the methods sections were between 372 and 2,674 words.

2. Compared to other sections in a research paper, the methods was about the same length as either the results or the discussion, and double the length of the introduction.

3. Review articles have the shortest methods sections overall, and experimental and quasi-experimental design articles have the longest methods sections.

4. In general, articles published in higher impact journals include a more detailed description of the materials and methods used.

Overall length of the methods section

Here’s a table that describes the length of a methods section in terms of words, sentences, and paragraphs:

Methods Section Length
Word CountSentence CountParagraph Count
Minimum7 words1 sentence1 paragraph
25th Percentile757 words31 sentences6 paragraphs
50th Percentile (Median)1,126 words45 sentences10 paragraphs
Mean1,278.8 words50.8 sentences11.1 paragraphs
75th Percentile1,620 words64 sentences14 paragraphs
Maximum18,517 words931 sentences336 paragraphs

From these data, we can conclude that the methods sections in most research papers are between 6 and 14 paragraphs (31 to 64 sentences).

If you are interested, here are the links to the articles with the shortest and longest methods sections.

The methods section constitutes 29.7% of the total word count in a research article, equivalent to the length of either the results or the discussion, and double that of the introduction [source: How Long Should a Research Paper Be?].

Length of the methods for different article types

The following table shows the median word count of the methods section for different study designs:

Study designNumber of studies in the sampleMedian methods word count
Case series140 studies567 words
Systematic review689 studies760 words
Meta-analysis1,481 studies849 words
Case-control443 studies931 words
Cross-sectional3,529 studies963 words
Case-report407 studies1,032 words
Cohort5,181 studies1,092 words
Pilot study686 studies1,140 words
Quasi-experiment144 studies1,177 words
Randomized controlled trial842 studies1,217 words

The data show that, in general, review articles (systematic reviews and meta-analyses) have shorter methods sections than average, and experimental and quasi-experimental designs require more detailed methods sections than average.

Length of the methods in different journals

In order to study the influence of the journal quality on the length of the methods section, I ran a Poisson regression that models the methods word count given the journal impact factor. Here’s the model output:

VariablesCoefficientStandard errorp-value
(Intercept)7.010<0.001<0.001
Journal impact factor0.049<0.001<0.001

The model shows that a higher journal impact factor is associated with a longer methods section. Specifically, a 1 unit increase in the journal impact factor is associated with an increase of 5% in the methods word count. For the median article, this means that a 1 unit increase in the journal impact factor is associated with an increase in 56 words in the methods section.

So the data suggest that, in general, articles published in higher impact journals include a more detailed description of the materials and methods used.

References

  • Comeau DC, Wei CH, Islamaj Doğan R, and Lu Z. PMC text mining subset in BioC: about 3 million full text articles and growing, Bioinformatics, btz070, 2019.

Further reading