Clear Comparisons Make Your Data Meaningful

Comparisons are crucial. They fill Abstracts, Results and Discussions: comparisons between groups, between theory and observation, between your study and others, and so on. With well-written comparisons, you demonstrate the clarity and logic of your analysis, and provide meaningful information; without good comparisons, your data lack meaning.

The example of an unclear comparison that I'm going to use comes from the abstract of a published, peer-reviewed paper. Because I don't want to embarrass the author, I've changed or omitted certain details, including the species, so this example does not present a real scientific finding. However, I have kept the structure of the comparison the same. 

An analysis of hematological indicators in puppies of breeds X and Y

Hematological indicators A, B, and C are used to determine the overall health status of dogs and to diagnose many diseases. The normal ranges of these indicators differ with age and sex, and recent studies also indicate that, in healthy adults of breeds X and Y, the values of these indicators can be outside what were previously considered to be the normal ranges for all dogs. However, it is not known if the levels of hematological indicators A, B, and C in healthy puppies of breeds X and Y can be outside the established norms. To answer this question, [...samples were taken from certain groups at certain times, etc.]. We found that, especially during the 2nd and 3rd months of life, the mean level of hematological indicator A was significantly higher in breed X (P < 0.05). [more details, which do not explain this comparison] 

Problem 1:
Higher than what? Higher than the established norms, than at birth, than in breed Y? The unknown and the research question suggest that the writer means "higher than the established norms", but we need to be sure. 

Solution:
Write complete comparisons: not "this was higher," but "this was higher than that." 

Problem 2: 
How much higher? Let's assume that the author is using "significantly" in the correct scientific sense, to indicate a "statistically significant" difference, not a "large" or "important" difference (Hofmann 2014). So we know that there probably is a real difference between the mean level of indicator A in breed X and whatever the author was comparing it to. But we don't know if this is a big or important difference. What if the difference is so small that it will be difficult to detect with the equipment that most veterinarians have? A "negative result" like this is still valuable, and the tendency not to publish negative results from medical studies is unscientific, unethical, and dangerous (Evans et al. 2011), but the result needs to be made clear. 

Solution: 
Remember, your readers need to know the size of the effect or the difference, not just that there probably is an effect or a difference (Evans et al. 2011, Nuzzo 2014). Be precise, and include information on both the size and the statistical significance, for example: 

"Although the difference was significant, the mean level of hematological indicator A was only slightly higher in breed X at 4 weeks of age than at 2 weeks of age (4 weeks [mean, standard deviation], 2 weeks [mean, standard deviation], P < 0.05)."  

Conclusion: 

Before you submit your paper, check it for these kinds of errors. It's easy to forget and write an incomplete or unclear comparison, and I've done it many times myself—in fact, a student found one in my writing just this Friday! 

References:  
Evans I, Thornton H, Chalmers I, Glaszou P. 2011. Testing Treatments: Better Research for Better Healthcare. Pinter & Martin, Ltd: London. p.88–89, 96–7, 163.
Hofmann, AH. 2014. Scientific Writing and Communication: Papers, Proposals, and Presentations. Oxford: Oxford University Press. p. 17, 270.
Nuzzo R. 2014. Statistical Errors: P values, the 'gold standard' of statistical validity, are not as reliable as many scientists assume. Nature 506:150-152.

Advice From Wiley-Blackwell Author Services: Repeat key words

The idea of trying to repeat words can seem strange to students of scientific English who come from non-English-speaking cultures. These students understand that a clear and direct style will help them to communicate with readers around the world, but they still feel uncomfortable repeating words.  The students' cultures often value varied and inventive expression more than English-speaking cultures do, and put less emphasis on clear and direct communication. Some of my Polish students have told me how their high school teachers took away points if they repeated words—"Never, never repeat words!" one student told me, shaking his finger as he imitated his teacher. The problem is that many synonyms in English have very specific meanings, so if you use a synonym, you change the meaning enough that your writing is no longer accurate and precise.

Therefore, it is important to repeat key words (the words that express the most important ideas in your article). This makes your writing clearer and more precise, and it helps connect your ideas so that other scientists can follow your thinking. It also has an additional benefit: if you repeat key words, you have a better chance of being read and cited.

I first saw this information on how repeating key words increases your chances of being cited on David M. Schultz's Eloquent Science blog. Schultz had posted a link to a page on Wiley-Blackwell Author Services which I excerpt below:

Optimizing your article for search engines will greatly increase its chance of being viewed and/or cited in another work…The crucial area for optimization is your article's abstract and title, which are freely available to all online…most [search engines] now scan a page for keyword phrases, giving extra weight to phrases in headings and to repeated phrases…In search engine terms, the title of your article is the most interesting element. The search engine assumes that the title contains all of the important words that define the topic of the piece and thus weights words appearing there most heavily. This is why it is crucial for you to choose a clear, accurate title. Think about the search terms that readers are likely to use when looking for articles on the same topic as yours, and help them by constructing your title to include those terms…The next most important field is the text of the abstract itself. You should reiterate the key words or phrases from the title within the abstract itself. You know the key phrases for your subject area, whether it is temporal lobe epilepsy or reconstruction in Iraq…Use the same key phrases, if possible in the title and abstract. Note of caution [author's emphasis]: unnecessary repetition will result in the page being rejected by search engines so don't overdo it. The examples below illustrate the difference between an abstract which is well-optimized and one which is not. [I recommend that you look at the examples in the original.]

In other words, as Schimel (2012, p. 5) has written, "It is the author's job to make the reader's job easy." Think about what words your readers are likely to search for. Put those key words in your title, and repeat those key words in your abstract. This will make it easy for readers to find your article. When you're writing your article, find the clearest, most precise words to explain your important ideas to your readers. Repeat those those key words; this will make it easy for your international readers in China, Argentina, Egypt or Germany — they don't want to be forced to use their dictionaries again and again. Remember, if you mean "bacteria", but instead you write "microbes", "microorganisms" or "prokaryotes", just to avoid repetition, your papers may be repeatedly rejected or returned for revision. Okay, I think I've repeated myself enough — after all, the Wiley-Blackwell Author Services page warns that we shouldn't overdo it ;-)





CALL FOR COMMENTS: Please help make Better English for Scientific Impact a better resource for teachers and students everywhere. If you find a good example of precise, clear scientific writing, post a reference to it in the comments and it may be included in a future lesson. If you have any questions, comments or suggestions, please post them too.

REFERENCE:
Joshua Schimel, Writing Science: How to write papers that get cited and proposals that get funded (OUP: Oxford, 2012), 5.