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Preparing Visual Aids
Once your presentation is complete, begin to identify the information you can present visually. Keep in mind that the fundamental purpose for visuals is to help the audience understand your message. This section will address what to present and how to design it. Listed below are some suggestions of information categories that can be effectively communicated as a visual:
- Title of presentation and authors
- Statement of the purpose or hypothesis
- A list of the essential steps in the methods
- Graphs, tables, and figures that show the major findings
- Clinical photographs or diagrams that illustrate key points or help explain content
- Summary of the conclusions
- Title of presentation and authors
- Essentials of the case presentation (history, physical examination, investigations)
- Clinical photographs demonstrating physical examination findings
- Important milestones in the patient's progress
- Key clinical decision points
- Lessons learned
In the past, it was customary to hire a professional artist to prepare visuals. These artists are located in the hospital or university's graphic arts department and will produce the visuals for a fee (usually charged to the department or training program). While the product is expertly done, it is expensive and time-consuming. Since the proliferation of personal computers and graphic arts applications, most physicians are capable of preparing their own visuals. If you have access to a personal computer and a graphics program like Power Point or Harvard Graphics, you can produce quality graphics, particularly after reviewing the following sections. If you have never used these applications, you may require some instruction, but you can easily master the necessary skills. The following guidelines will assist you in producing high-quality, effective visuals.
Preparing Slides of Text
Slides of text (outlines, lists, sentences) make up 75% of all visuals. An effective text slide can highlight important concepts, sequences; poorly designed text slides can frustrate and confuse the audience. The following rules will help ensure that the visual is effective:
1. Follow "The Rule of Seven" by limiting text on a slide to no more than 7 words per line, and no more than 7 lines per slide.
2. Be concise; avoid jargon and abbreviations.
3. Use the largest font available.
4. Limit the font sizes to three per slide.
5. Use only one font style throughout the presentation.
6. Use bullets to highlight individual points in the text.
The text slides should be informative but not too busy. Too much text will distract the audience from your presentation as they attempt to read the slide. The slide should be easily readable from the back of the room. The smallest text font barely acceptable font is 18-point; 28-point is better, and 32-point is best. There is a natural hierarchy of font sizes for a text slide (title-44-point font, main headings-32-point font, subheadings and text-28-point font). While its best to kept the format of the slides consistent from one slide to the next, it is acceptable to use italics or boldface for emphasis.
Despite what you frequently hear at meetings, there is no excuse for, " I know this is a bit busy…" or, " You probably can't read this…" To illustrate these concepts, see the examples of poorly designed and improved text slides.
Color can add interest to a presentation, highlight important points, and adds to the "professional quality" of the visuals. Inappropriate use of color can diminish the effectiveness of a presentation by making it difficult to read. The four rules of color are:
1. Use the same color scheme throughout the presentation for titles, text, and background.
2. Do not mix colors within a text sentence.
3. Use no more than four different colors per slide.
4. Choose color combinations that contrast well.
The slide is a supplement to your presentation and should not distract from your presentation. Altering the color scheme from one slide to the next is distracting to the audience and is to be avoided. Therefore, keep the text the same color from line to line and slide to slide. Similarly, the titles and subtitles should be the same color from slide to slide. It is permissible to alter the color of an occasional word for emphasis (for example, a red word in a string of black text). The color of the text should be chosen to contrast with the background. For example, yellow on blue is easily read due to the sharpness in contrast, whereas yellow on white may be indistinguishable due to low contrast. Low-contrasting colors be readable on-screen but wash out when projected on a large screen. If in doubt, test your combinations by projecting them onto a screen, but give yourself enough time to change the color scheme if necessary.
The purpose of a table is to present complex data, to demonstrate patterns and relationships, and to present exact data. In general, tables are less dramatic than graphs of the same data and should be used when graphs or figures can't make the point.
The three rules of designing tables as a visual are:
1. Make it simple.
2. Make it fit.
3. Make your point.
The table must be able to make your point quickly. The longer the audience spends reading the table, the less they will listen to you. Reduce the content of a table to its essential elements, and make sure that it remains readable from the back of the room. Of course, the table should fit onto the screen and not project off the side or the bottom. Concentrate on including only the data that makes your point and refrain from including extra data just because you collected it. It is better to make a few points well than many points superficially.
Tables have four essential elements: title, column headings, row headings, and field. More sophisticated tables may have other elements including a box heading, stub heading, and footnotes. Finally, the table should be able to "stand alone"-it can be understood in its entirety without explanation. One way to assess understandability is to have your tables reviewed by a colleague unfamiliar with your presentation. If your colleague can quickly and correctly interpret the purpose and content of the table without your explanation, it has passed the "stand-alone" test. The following paragraphs describe the essential elements of a table.
Title: The title fully explains the purpose of the table or the relationship between the rows and the columns of the table. The title should not be redundant to the column or row headings (see below) and can be supplemented by a footnote if absolutely necessary. For example, "The Relationship Between Medical College Aptitude Scores and Performance on the Licensing Examination" is sufficiently descriptive that it can "stand alone" as a title as compared to "MCAT Scores." The latter title fails to describe the essential relationship that the table is trying to convey.
Column Headings: Column headings identify the type of data within the column and the unit of measurement. Sometimes columns can indicate two different formats for the same data, such as number and percent, usually presented as N (%). An example of a field entry within this column would appear as 33 (18), where 33 = N, or the frequency count, and (18) = (%), the percent of the whole.
Row Headings: Row headings typically represent the category of data. Headings and subheadings can be used and are distinguished by appropriate use of indentation.
Field: The field is simply the data within the table organized into rows and columns. A well-designed table has the data entries centered below the column heading. All data cells (the points where rows and columns intersect) need an entry. If the data point is zero, enter a 0, if it is missing, enter dashes (-). When entering numbers, simplify large numbers with an appropriate scale in the column heading and avoid "pseudo-precision" by appropriately rounding numbers to the closest integer or decimal place.
Look at the example to understand the essential elements of a table. A second example illustrates and compares a poorly constructed table to an improved table. After completing your tables, use the Table Checklist to make sure you tables meet the quality criteria suggested in this article.
(All examples in the "Making Figures" section are available to be downloaded as an Adobe Acrobat PDF and as a PowerPoint presentation)
A figure is any type of illustration other than a table. Graphs, charts, diagrams, and photographs are all examples of figures. Figures can quickly illustrate, clarify, or emphasize key relationships between categories and numbers, revealing structural relationships and processes, such as decision making. Well-designed figures convey only the essential facts while visually distracting details are omitted. This is illustrated in the two examples; example 1 has too much distracting detail, whereas example 2 is stripped down to the essentials.
Figures must be easy to read and understand quickly and should require very little explanation during the presentation. Like tables, figures should be able to pass the "stand-alone" test. The style used to construct the figure should be consistent throughout the presentation, including font style and size, color scheme, and organization. There are several types of figures that can represent data in a particular way. Take care to pick the right type of figure for your data and the point you want to make. Descriptions and illustrations of the most common types of figures are presented below.
Line Graphs: Line graphs show continuous change over time. The ordinate (Y-axis) typically depicts quantity and the abscissa (X-axis) depicts time. By plotting several lines on the same graph, it is possible to compare the trends of several variables. As a rule, the number of lines should be restricted to no more than four, particularly if the lines intersect, because it becomes too difficult for the audience to interpret. See an example of a line graph.
Bar Graphs: Bar graphs consist of simple horizontal or vertical bars, each representing one type of data. Like line graphs, bar graphs show changes in variables over time; in contrast, the data is not continuous (like death rates) but discrete (like symptom scores). More often, bar graphs compare quantifies of different variables, but not over time. Examples include ratings of questions on a survey or number of patients with various symptoms. Variations of the same measure can be compared by stacking different colored bars on top of each other (particularly if they sum to 100%) or compared side by side. Examples of stacked data might include the number (or percentage) of men and women in a study (the two sum to 100% of the study participants) and an example of a side-by-side comparison might include number of patients with Class III and IV congestive heart failure (probably won't add up to 100% of all patients with heart failure). See the examples of a simple bar graph and a stacked bar graph.
Pie Chart: Pie charts compare the parts to the whole and visually display percentages and proportions. The circular pie represents the whole and the size of each wedge of pie shows the components share. Pie charts have the advantage of allowing the audience to quickly visualize proportional relationships. Two rules for pie charts are:
1. Show no more than six "slices."
2. Position the largest slice at the 12 o'clock or 6 o'clock position.
When more than six slices in a pie chart are displayed, the individual parts and legends become too difficult to discriminate from each other. Positioning the largest slice at the top or bottom position of the pie graph emphasizes its importance to the whole. See the example of a pie chart.
Scatter Graphs: Scatter graphs consist of dots on a graph that can be used as an analytical tool. The dots usually represent the intersection of two bits of data showing the relationship of one variable to another. See the example of a scatter graph.
After completing your figures, use the Figures Checklist to make sure your figures meet the quality criteria suggested in this article.