Elements of Graphing Data

M PREFACE .................................. 1 Chapter1.INTRODUCTIO N............... .............3 1.1TheContentsofthe Book.......... .........3 Chapter2:PrinciplesofGraphConstructio n.. .3 Chapter 3:Graphical Methods... ........... 4 Chapter 4:Graphical Perception ........... . 7 1.2ThePowerof GraphicalDataDisplay..........9 l1.3TheChallengeofGraphicalDataDisplay........12 Aerosol Concentrations .......... ......... 12 BrainMassesandBodyMassesof  Animal SPECIES ........... ............ 13 W1.4 SourcesandGoals................ .........17 Pr1nc1p lesof Graph Construction.......... . 17 Graph1cal Methods.. ........... ......... 18 Graphical Perception .................. .. 18

Chapter2.PRINCIPLESOF GRAPHCONSTRUCTI ON.......21 2.1 Termirwlegy ....»......,. .........__ , ____ 21 2.2 Clear Vision ............................. 24 2.3 Clear Understanding ....................... 56 2.4Scales............ ............ ...,......68 2.5 General Strategy........ ............. ..... 89 W 2.6AListingofthePrinciplesofGraph3 Constructi on.............. r...... I ........ 100 Chapter 3.GRAPHICAL METHODS .......... ............ 103 .3.1 GeneralMethods:Logarith msandResiduals.....104 3 Logarithm s................ ............104 aLegBase2andLogBasee ............ .....106 Graphing Percent Change... ............ .. 111 Residuals........ ...,......... ........ 11 4 TheTukeySum-D ifferenceGraph.... .......118 3.2Oneor MoreCategorie sof Measurem entsof  OneQuantitativ eVariable:Graphing Distributio ns...........,... ............. . 123 PointGraphsand Histograms...... ........124 PercentileGrap hs.........ji ............ . 127 BoxGraphs......... ............ .......129 PercentileGrap hswithSummaries..........134 PercentileComp arisonGraphs.............135 g A3.3OneQuantitativeVariableWithLabels:3 DotCharts............ ............ .......144 OrdinaryDot Charts.................... . 144 ‘ Two-Way,G rouped, andMulti-Valued VDot Charts........... ............. .. 151 3 3.4Two QuantitativeV ariables __________________ 154 M Overlap: Logarithms,Residual s,Moving, Sunflowe rs,littering, andCircles .......... 154

Box Graphsfor SummarizingDistr ibutions ofRepeatMeasurementsofa" Dependent Variable ........... ......... 163 StripSummarie sUsing BoxGraphs.......... 166 Smoothing: Lowess. ........... ......... 167 TimeSeri es: Connected, Symbol, Connected MSymbol,andVerticalLineGraphs.........178 TimeSeries:SeasonalSubseriesGraphs......186A An Equally-Spaced Independent Variable withaSingle-ValuedDependentVariable...188 WiStep FunctionGrap hs...........,.........189 3.5Twoor MoreCategorie sofMeasurementsof  TwoQuantitativeVariables:Superposition4 andIuxtaposi tion ........... ........... ... 191 Superpo sedPlottingSymbols...... ........191 Superpo sedCurvesinBlack andWhite.......196 Iuxtapo sition.............. .......;.Q,. .. 198 Color ........... ............ ......... 205 3.6Threeor MoreQuantitat iveVariables..........208 Framed-R ectangleGraphs....i. ........... . 208 W1 ScatterplotMatrices............ .........210 AViewoftheFuture: High—Int eractionW Graphica l Methods....... ............ . 213 .3.7 StatisticalVariation............. ............ 218 Empirica lDistributionoftheData...7. .......219 Sample-to —SampleVariatio nof aStatistic...... 222 One¥Stan dard-Err orBars.......... A........223 . Two-Tier edErrorBars.............. ......226 Chapter 4.GRAPHICAL PERCEPTION..... ............. .. 229 WA4;1 CognitiveTasksandPerceptu alTasks..........230 4.2TheElementsofthe Paradigm........... .....233 E ,Elementary Graphical-Percep tionTasks....... 233

Distance........ ...,...... Q ........... 238 Detection ........... ........... ....... 239 4.3 Theory andExperimen tation. ............ .... 241 Weber’sLaw......... ............ ......241 Stevens' Law ........... ............. .. 243 AngleIudgm ents............. ..........245 TheAngleContamin ationofSlopey Iudgments.. ............ ........... ... 245 Experim entsinGraphicalPerception.... .....247 summaryand Discussion .............. ... 254 4.4ApplicationoftheParadigmtoDataDisplay.....255.9 Slopejudgme nts:GraphingRateofChange... 255 LengthJudgments:DividedBarCharts......259 AngleJudgme nts: PieCharts.............. 264 Cognition .......... ............ ....... 264 DistanceandDetection............ .......265 _ 9 Detection: SuperposedCurves. ............ 271 4 Area............ ............. ........ 278 A DensityandLength:StatisticalMaps........284 Residuals........ .............A........288 DotChartsandBarCharts................291 Summation.. ............ . ’............ . 294W 2REFERENCES................ . .......A......295 GRAPHINDEX........ ............ .........307 rnxrINDEX....... ............. .A. .·.....,. .ais