Appendix D: Writing Comparisons

College classes often ask you to write comparative analyses in which you compare two or more items in a way that offers some meaningful conclusions.  You can compare almost anything – even porcupine and mushrooms – as long as you have a clear reason for your comparison (a thesis) and logical criteria for comparing the items.  For example, although porcupines and mushrooms seem to have very little in common (different life forms) you might compare how both porcupines and mushrooms have developed similar self-preservation methods to avoid predators.  In order to compare two items, they must have obvious differences, but interesting similarities – or, conversely, obvious similarities, but interesting differences.  Your reason for comparing can often be expressed by clearly articulating these interesting similarities or differences.

In technical communication, comparisons are helpful when discussing options, such as in recommendation or problem-solving reports, with a goal of recommending the option that best meets the criteria for resolving a matter. In such documents, options would be compared using the criteria as the basis for comparison with the goal of convincing the reader of the best solution.

This chapter will review

  1. the basic grammar of comparative sentence structure, and
  2. the overall comparative structures.

1. Comparative Grammar

We frequently engage in making comparisons in daily life. This leads to a sort of “shorthand” in the way we express comparisons. This shorthand might be understood in a conversational way, but in formal writing, we must adhere to certain grammatical standards. A correct comparative sentence should adhere to the following rules:

  1. Clearly identify the things being compared.
  2. Ensure the compared items are equivalent and comparable.
  3. State the specific criteria for comparison.

These rules might seem obvious, but we often break them in our informal conversational comparisons. For example, the following sentence wants to compare the difficulty of dealing with the peels of apples and oranges, but grammatically compares apple peels to “my lab group,” which are not equivalently comparable.

Compared with apple peels, my lab group found orange peels more difficult to deal with.

How would you fix this sentence to correctly express the comparison of apple peels to orange peels?

They say you can’t compare apples and oranges, but you actually can as long as you have established their equivalence, have stated a purpose, and defined clear criteria for comparison.  For example, you CAN compare apples to oranges, but you cannot compare apples to fruit.  You can compare fruit to vegetables, but you cannot compare fruit to carrots.  These are non-equivalent.  Non-equivalent comparisons are often a result of faulty sentence structure.

Here is an example of an effective comparative topic sentence:

There are significant differences between apples and oranges in terms of their culinary uses, nutritional content, and growing needs. 

Comparative sentences can fail for several reasons:

  1. They are incomplete (do not clearly identify the two items being compared):
    • Apples grow better in northern climates.
    • Oranges have twice the vitamin C content.
    • Apples are considered more effective “comfort food.”
    • This design is better.
  2. They are too vague (they don’t provide enough meaningful information about the items):
    • There were some differences in the characteristics of apples and oranges.
    • There were some similarities in the teamwork between the two labs.
    • Lab 2 was better than lab 1.
  3. The comparisons are faulty (often missing information, a sentence structure error, or idiom error):
    • This process of juicing oranges is different than apples.
    • Compared with the first lab exercise, my team and I have a more professional approach toward our common goal.
    • Cooking apples is easier as opposed to oranges.
    • This lab helped us understand the value of teamwork as against individual work.

Exercise D-1

Try writing 2 or 3 comparative sentences, making sure you follow all three rules, and watching out for incorrect vernacular phrasing.



2. Comparative Structure:  Alternating vs Block Structures

Comparisons are used to compare options in recommendation and other technical reports. Just as there are rules at the sentence level, there are also guidelines for comparative paragraph and report structure. Alternating (also called Point-by-point) and Block (also called Whole-to-whole) structures are common ways of organizing a comparative analysis, and the structure you use will depend on what, how, and why you are comparing.  Let’s say you are writing a comparative analysis of two types of wind turbines. Your overall purpose might be to analyze them to determine which is most economical to operate.

  1. Alternating Style arranges the structure based on the criteria for comparison. One criteria might focus on characteristics; the second criteria might focus on performance, while a third might focus on maintenance.
  2. Block Style arranges the structure based on the items being compared (each turbine).  Each paragraph will focus on one of the turbine types, and may discuss more than one criteria for comparison.  For example, the first section might focus on one turbine in detail, and might discuss performance and maintenance. The next section would focus on the other turbine, using the same criteria for comparison: performance and maintenance.

Often, Alternating structures work well for this kind of comparison, as you can structure your analysis based on a discussion of each factor in turn. You might choose to organize your analysis in a Block style, if the turbines are quite different and you are focusing on different criteria for comparison for each turbine. The table below shows simplified outlines for each structure:


Table D-1 Simple Outlines of Block and Point-by-Point Structures

Block Style Alternating Style

Introduce the turbines being compared and state the purpose of your comparison (purpose statement)

Item 1 (Turbine A)

  • In-depth analysis of item 1, focusing on several criteria (may need more than 1 paragraph)

Item 2 (Turbine B)

  • all the things you want to say about item 2
  • you may compare a bit to item 1

Direct Comparison

You will likely need an extra paragraph here for direct comparative analysis based on the discussions in the previous sections.



Introduce the turbines being compared and state the purpose of your comparison (purpose statement).

Criteria 1 (Characteristics)

  • Article A directly compared to Article B in terms of criteria 1

Criteria 2 (Performance)

  • Article A directly compared to Article B in terms of criteria 2

Criteria 3 (Maintenance)

  • Article A directly compared to Article B in terms of criteria 3



PROs and CONs

If  your items are different enough that you aren’t using the same criteria for comparison, use Block style.  But this can end up being a bit repetitive in that you have to remind your reader of your analysis when you get to the direct comparison part at the end.

PROs and CONs

If you have the same criteria for each item, this is the most economical way to organize your report.  But it can sound a bit “ping-pong” like if you are not careful with transitional words and phrases.



Block and Point-by-point structures are helpful principles for organizing your ideas, but keep in mind that you do not have to rigidly follow these outlines. You can mix these up a bit and use hybrid methods.  Examine the excerpt below, from Douglas Rushkoff’s book Program or Be Programmed: Ten Commands for a Digital Age (2011).  Identify where the author has used block style, point-by-point style, and a mixture of the two. Also, note the use of comparative transitional words and phrases (highlighted for emphasis).

Sample Comparative Passage – by Douglas Rushkoff

The difference between an analog record and a digital CD is really quite simple. The record is the artifact of a real event that happened in a particular time and place. A musician plays an instrument while, nearby, a needle cuts a groove in a wax disk….  The sound vibrates the needle, leaving a physical record of the noise that can be turned into a mold and copied. When someone else passes a needle over the jagged groove over one of the copies, the original sound emerges. No one has to really know anything about the sound for this to work. It’s just a physical event—an impression left in matter.

A CD, on the other hand, is not a physical artifact but a symbolic representation. It’s more like a text than it is like a sound. A computer is programmed to measure various parameters of the sound coming from a musician’s instrument. The computer assigns numerical values, many times a second to the sound in an effort to represent it mathematically. Once the numerical – or  “digital – equivalent of the recording is quantified, it can be transferred to another computer, which then synthesizes the music from scratch based on those numbers.

The analog recording is a physical impression, while the digital recording is a series of choices. The former is as smooth and continuous as real-time; the latter is a series of numerical snapshots. The record has as much fidelity as the materials will allow. The CD has as much fidelity as the people programming its creation thought to allow.  The [configuration of] numbers used to represent the song – the digital file – is perfect, at least on its own terms.  It can be copied exactly, and infinitely.

In the digital recording, however, only the dimensions of the sound that can be measured and represented in numbers are taken into account. Any dimensions that the recording engineers haven’t taken into consideration are lost. They are simply not measured, written down, stored, and reproduced. It’s not as if they can be rediscovered later on some upgraded playback device. They are gone.

Given how convincingly real a digital recording can seem—especially in comparison with a scratchy record – this loss may seem trivial. After all, if we can’t hear it, how important could it be? Most of us have decided it’s not so important at all. But early tests of analog recording compared to digital ones revealed that music played back on a CD format had much less of a positive impact on depressed patients than the same recording played back on a record. Other tests showed that digitally recorded sound moved the air in a room significantly differently than analog recordings played through the same speakers. The bodies in that room would, presumably, also experience that difference – even if we humans can’t immediately put a name or metric on exactly what that difference is.

Rushkoff, Program or Be Programmed: Ten Commands for a Digital Age, pp. 52-54




Rushkoff, D. (2011). Program or be programmed: Ten commands for a digital age. Soft Skull Press, pp. 52-54.


Icon for the Creative Commons Attribution 4.0 International License

Technical Writing Essentials Copyright © 2019 by Suzan Last is licensed under a Creative Commons Attribution 4.0 International License, except where otherwise noted.

Share This Book