Using comparisons in scientific writing

In the results section of most scientific or medical journal articles, the authors will try to describe at least one comparison. Perhaps there will be a comparison between an experimental group and a control group. Or, a group of patients treated with surgery will be compared with patients treated with medicine. The words you use to present your comparisons are crucial if you want your readers to understand your results.

There are several ways to express comparisons, and some are easier to understand than others. There are some general rules to follow.

Use as few words as possible

Comparisons are relatively simple concepts. Symbolically, we can express the concept “X is greater than Y” simply as X > Y. The result here is conveyed in three symbols. It should never be necessary to use 25 words to express such a simple idea.

Worse: In terms of weight gain, the results showed that compared with the control group, the experimental group gained more weight (20 words).
Better: Weight gain was greater in the experimental group than in the control group (13 words).

Use p-values

If a comparison involves statistical significance, use p-values in parentheses, rather than using words to tell the reader there is statistical significance.

Worse: X was greater than Y and the difference was significant.
Better: X was significantly greater than Y (P < 0.05).

Be careful choosing comparison words

English provides many words for making comparisons. Some are better than others for scientific writing. For example, modern scientific writers often use the terms “increased” and “decreased” when they mean simply “higher” or “lower”. The choice is important because “increased” and “decreased” imply that an agent caused something to increase or decrease.

Whereas this in fact may be the case, most of the time in scientific investigation we cannot be sure whether a value increased or decreased because it was altered by some factor (e.g., a drug or reagent) or whether the values went up or down for another reason, or for no reason at all.

Worse: Weight gain was increased in the experimental group compared with the control group (implying that the experimental intervention caused weight gain, when in fact we do not know why the weights were higher in one group or the other).
Better: Weight gain was greater in the experimental group than in the control group (here, we are only stating the result, without implying that we know the reason for the result).

The bottom line is that it is more accurate, and scientifically sound, to use words such as “higher” and “lower” than “increased” and “decreased”.

Scales with apples and oranges

The words you use to present your comparisons are crucial if you want your readers to understand your results.

Use the comparative preposition than

In the previous example, we used the preposition than to express a comparison. You will find that using this word will make your results sections easier to read and understand.

Worse: When it comes to weight gain, compared with the control group, the results showed that insulin increased weight gain in the experimental group.
Better: Weight gain was greater in the insulin-treated group than in the control group.

Worse: Compared with the patients without Boney–Maroney syndrome, prolactin levels were significantly increased in Boney–Maroney patients.
Better: Prolactin levels were higher in Boney–Maroney patients than in normal controls.

Upregulation and downregulation

In modern scientific writing, the terms upregulation and downregulation (sometimes expressed with hyphens: up-regulation, down-regulation) are becoming increasingly accepted by editors and reviewers. The words were originally used to describe the expression of receptors in response to stimulation by ligands. Over time, the words “upregulation” and “downregulation” have become synonymous with “increase” and “decrease” with respect to any and all processes.

Although these terms are generally accepted, they are misleading. This is because upregulation and downregulation retain some of the meaning they had when they referred only to receptor regulation. The implication is that values that go up and down are compelled to do so by some (known) external force. Nevertheless, in scientific writing, we are never certain why values go up and down, we can only draw inferences as to the causes. We can describe associations; however, associations are not causes.

If you are writing about receptors, “upregulated” and “downregulated” are perfectly fine to use. If you are writing about anything else, and you want your results to be clear, concise, and (most important) scientifically sound, use “higher” and “lower”.

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