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352 PART V: Analyzing and Reporting Researchthe data picture is altered. Minimally, by experimenting with different waysto visualize our data set, we become more familiar with it. Which visual representationreveals the most about our data? What do we learn about our datawhen we compare plots with the axes defined differently? Is a polygon orhistogram more informative? A picture not only is worth a proverbial 1,000words, but also it can quickly summarize 1,000 numbers. As we become morefamiliar with different pictures of our data, we learn that some pictures arebetter than others.The data from our example vocabulary study represented the number of correctmeanings identified out of a possible 191. Because participants withoutknowledge of the correct answer can be correct by chance on multiple-choicetests, a standard correction for guessing was applied to individual responses.However, two typographical errors appeared in the booklets given to theolder adult group, so these items were deleted from further analysis. Also,examination of the test booklets revealed that several of the older participantsomitted a page when working through the test booklet. Thus, the number ofpossible words was reduced for these individuals. Because of these problems,the data were transformed to percent correct to account for differences in thetotal number of possible responses among participants.After cleaning the data set, the researchers obtained the following data in thefirst stage of the analysis. These data are expressed in terms of percent correctmultiple-choice performance for college students and older adults.College (n 26): 59, 31, 47, 43, 54, 42, 38, 44, 48, 57, 42, 48, 30, 41, 59, 23, 62,27, 53, 51, 39, 38, 50, 58, 56, 45.Older adults (n 26): 70, 59, 68, 68, 57, 66, 78, 78, 64, 43, 53, 83, 74, 69, 59,44, 73, 65, 32, 60, 54, 64, 82, 62, 62, 78.Key ConceptStem-and-Leaf Displays A stem-and-leaf display is particularly useful for visualizingthe general fea tures of a data set and for detecting outliers (Tukey, 1977).A stem-and-leaf display obtains its name through the convention of using leadingdigits in a numerical array as “stems” and trailing digits as “leaves.”The following is a stem-and-leaf display for the college student data fromour example vocabulary study:2* 32 73* 013 8894* 122344 57885* 01345 678996* 2The leading digits are the first or tens’ digits (e.g., 2-, 3-, 4-,) and the trailingdigits are just that, those that trail the leading or most significant digits; in this