Online Technical Writing: Information Structures
Comparison

In technical writing, comparisons can be very important. Short comparisons to similar or familiar things can help readers understand a topic better; comparisons can also help in the decision process of choosing one option out of a group. An extended comparison, which is the focus in this section, is one or more paragraphs whose main purpose and structure is comparison.

Extended comparisons can be informative or evaluative. An informative comparison seeks to compare the topic to something similar or familiar to help people understand the topic or, in some cases, to help people understand both better. An evaluative comparison seeks to recommend one or more of the options by comparing them. This is the focus of the types of reports discussed in the section on recommendation reports, feasibility reports, evaluative reports.

Note: Be sure and check out the examples of comparison that accompany this chapter:

• Nuclear Power Plants
• Wind Electrical-Power Generators

When you write an extended comparison, you must start by identifying the specific ways in which you are going to compare the things you plan to write about. These points of comparison are like categories of comparative detail. For example, in an evaluative comparison of VCRs, you'd probably want to compare the best four or five machines according to cost, programmability, reliability, special editing features, and so on. If you don't start by identifying the points of comparison, your comparison can become uneven--for example, you might say that VCR Model 1 is easy to program but not say anything about the programmability of VCR Models 2, 3, or 4.

In evaluative comparisons, you must also define the requirements, or the criteria. For example, you might have a maximum cost of $150 for the VCR. You might want the machine be very easy to program and have good ratings in terms of its reliability. And you might require that the VCR have a certain special editing feature. These are all requirements--some are numerical like cost; some are based on scales such as ease of use; and some are simple yes/no values--either the machine has the feature or not.

Also for evaluative comparisons, you may have to rank the requirements--the most important to the least important. In fact, you may have to devise a statistical method for determining the winning option.

One of the most important concepts to learn in writing comparisons has to do with organizing the contents. There are two basic ways to organize a comparison--the whole-to-whole approach and the point-by-point approach. To get a sense of how these two approaches work, take a look at Figure G-12. In the whole-to-whole approach, details about each of the options being compared are lumped together. This is our natural tendency--however, it does a sloppy, uneven job of stating the comparisons. The better way is to use the point-by-point approach. In the schematic diagram in Figure G-12, you'd have one paragraph comparing the costs of Models A, B, and C; then another paragraph comparing the warranties of the three models; and so on.

Use the point-by-point approach unless something about your topic, purpose, or audience dictates otherwise. With the whole-to-whole approach, the comparison is often uneven--you might forget to tell about the warranties for Model B; you might neglect to state the actual results of comparison--that Model C is better in terms of special features. In the whole-to-whole approach, writers often leave the actual comparisons up to the reader, thinking that just supplying the raw data is enough.

In the point-by-point approach, each of the comparative sections should end with a conclusion that states which option is the best choice in that particular category of comparison. Of course, it won't always be easy to state a clear winner--you may have to qualify the conclusions in various ways, providing multiple conclusions for different conditions.

Figure G-12. Schematic view of the whole-to-whole and the part-by-part approaches to organizing a comparison. Unless you have a very unusual topic, use the point-by-point approach.

Figure G-13. Short paragraph-length comparison.

As with causal discussions, comparisons are not distinctive because of a certain kind of content. instead, it's the special transitional words that make comparative writing work: for example, "similar, "unlike," "more than," "less than," and other such words that draw readers' attention to comparisons and highlight the results of the comparisons. Notice how many are used in Figure G-13.

When you write comparisons, take special care to use these transitional words. Emphasize the similarities and differences--don't force readers to figure them out for themselves.

Figure G-14. Schematic view of comparisons. Remember that this is just a typical or common model for the contents and organization--many others are possible.

Comparisons don't call out for any special format; just use headings, lists, notices, and graphics as you would in any other technical document. For details, see:

• Headings
• Lists
• Notices
• Graphics

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