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Strong evidence has been given in the past for the superiority of flowchart style procedures over prose style procedures. A study by Gregory Krohm ("Flowcharts Used for Procedural Instruction", Human Factors, 1983, 25(5), 573-581) attempted to isolate those features of flowchart design that affect performance. The two key findings of the study were that (1) flowchart orientation consistent with standard reading orientation (i.e., left-to-right, top-to-bottom) produced significantly better performance than other orientations and (2) the number of alternatives in each decision block had no effect on performance.

In designing CRT displays with a combination of graphics and text, the question of how much text needs to be displayed at one time often arises. R. L. Duchnichy and P. A. Kolers ("Readability of Text Scrolled on Visual Display Terminals as a Function of Window Size", Human Factors, 1983, 25(6), 683-692) produced some interesting data on the question of how much text is enough. With no variation in comprehension, Duchnichy and Holers found that text displayed on 67-100% of the screen length resulted in 25% faster reading than when it was displayed on 33% of the screen length. In addition, they found that texts with 80 characters/line produced 30% faster reading than with 40 characters/line and displaying 20 lines of text caused no faster reading of the material than displaying 4 lines of text. The conclusion is that when designing a display with limited space for text, display 4 lines of the text, with 80 characters per line, at least 2/3 the width of the screen.

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This year's Fall meeting for the Center for Operator Performance will be October 7-10 in Houston, TX. For more information, please contact Lisa Via. Guests are always welcome!


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David Strobhar's book, "Human Factors in Process Plant Operation," is now available in both hardcover and Kindle e-book.

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