OBJECTIVESAfter completing this chapter, you will:■ Design and draw the following types of charts and graphs:rectilinear, surface, column, pie, polar, nomographs, trilin-ear, flow, distribution, and pictorial.■ Use a computer-aided design and drafting system to designand draw a chart from engineering specifications andsketches.1WEB CHAPTER Engineering Charts and Graphs3THE ENGINEERING DESIGN APPLICATIONGiven the following statistical data, design a rectilinearchart that will represent the information.Projected population of the United States from 1985to 2165. The source is World Bank data, projected assum-ing constant fertility and migration. The year is followedby the population in millions: 1985—238, 1995—255,2005—269, 2015—282, 2025—290, 2035—291,2045—287, 2055—283, 2065—279, 2075—273,2085—269, 2095—264, 2105—259, 2115—255,2125—251, 2135—247, 2145—243, 2155—240,2165—239.Step 1.Establish the range of units. In this case the low-est unit in years is 1985 years and the highest is2165 years. The lowest unit in population is238 million and the highest is 291 million.Step 2. Determine the vertical scale to accommodatethe range; for example, 230 to 300 million asshown in Figure 1.Step 3. Determine the horizontal scale. In this case thereis a set of data every ten years. The horizontalscale will be divided into units representing ten-year modules. It is best to make the horizontalscale approximately equal to the vertical unitswithout crowding. In this case there are morehorizontal than vertical units, so the ten-yeardivisions will be closer than preferred; however,the thirty-year divisions will be the main units asshown in Figure 2.Step 4. Plot the points and draw the curve as shown inFigure 3.Step 5. Complete the chart by labeling the title and anyrequired captions. (See Figure 4.)300290280270260250240230FIGURE 1 ■ Step 2—determine the range for the vertical scale units.3002902802702602502402301985 2015 2045 2075 2105 2135 2165FIGURE 2 ■ Step 3—determine the horizontal scale and estab-lish the grid.(Continued)Charts are graphic representations of any measurable data.Charts, graphs, and diagrams are all synonymous with thegraphic representation of numerical data. Charts may be morespecifically defined as illustrations that give information thatwould otherwise be arranged in a table (tabular form). Graphsand diagrams are a series of points, a line, a curve, or an arearepresenting the comparison of variables. The advantage ofcharts and graphs is that technical data may be shown in amanner that quickly and graphically communicates the infor-mation.Professionals in any field can use charts and graphs tographically explain or demonstrate the results of statistics. Sta-tistics is the science of the collection, arrangement, and inter-pretation of quantifiable information. Statistics has two areas orbranches: descriptive statistics and inferential statistics. Descrip-tive statistics is the summarizing and organization of data.Inferential statistics includes making inferences (drawing con-clusions) about a whole population based on informationobtained from a sample. Many engineers, quality-control peo-ple, and managers are beginning to understand that to reallyinterpret data, they need the statistics and a picture of the datain the form of a chart or graph. Many people have difficultyunderstanding and interpreting statistical data unless the quan-tities are shown on a chart or graph.The accurate preparation of charts and graphs requires adegree of knowledge of the topic related to the data and anunderstanding of where, how, and why the chart is used. Thereare two fundamental applications for charts: analysis and pres-entation. Analytical charts are used to analyze, examine, andexplore data, or the information is used to calculate specificrequired values. Presentation charts are generally more artisticin appearance and are used to demonstrate or present informa-tion. Presentation charts are used in advertising and may bepictorial for easy communication of data for laypeople. Whilethere may be two classifications of charts, there is a crossover.For example, analytical charts may be used for presentation,and presentation charts often contain analytical data.ASA According to the American Standards Associationdocument ASA Y15.2, the following questions should beanswered before a chart design is started:1. What is the general purpose of the chart?2. What kind of data are to be presented?3. What features of the data is the chart to identify?4. For what audience is the chart intended?5. What method will be used to show the chart to the audience?The selection of the specific type of chart is the designer’schoice. Not all chart design questions are applied to each chart.Some charts may be designed to focus on one or more of therelated design questions. One of the most important factors inchart design is simplicity. Keep the chart as simple as possibleby avoiding the presentation of too much information or detail.Charts may be designed for any purpose to accurately com-municate numerical data from a simple line format to a pictorialpresentation. The selection of the chart type depends on theaudience, the intent of the presentation, and the type of data.The basic types of charts include rectilinear (line) charts, sur-face charts, column (bar) charts, pie charts, polar charts, nomo-graphs, trilinear charts, flowcharts, distribution charts, and pic-torial charts.RECTILINEAR CHARTSRectilinear charts, also known as line charts, are the most com-mon type of chart used for the presentation of analytical data.The rectilinear chart is commonly set up on a horizontal andvertical grid where the horizontal axis or scale representsamounts of time or other significant independent values. Thevertical axis identifies the dependent quantities or valuesrelated to the horizontal values. The horizontal axis is calledthe X axis or abscissa, and the vertical axis is called the Y axisor ordinate. The line formed by connecting the data elements iscalled the curve. (See Figure 5.) Rectilinear charts are referredto as a slope curve when the data represent points in time that2 ■ Engineering Charts and GraphsTHE ENGINEERING DESIGNAPPLICATION (continued)3002902802702602502402301985 2015 2045 2075 2105 2135 21653002902802702602502402301985 2015 2045 2075YEARSWORLD BANK DATA PROJECTED ASSUMINGCONSTANT FERTILITY AND MIGRATIONPOPULATION IN MILLIONSPROJECTED POPULATION OF THEUNITED