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Chapter 2 and Infographics Project Graphs: Good, Bad & Ugly
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A visual presentation of data Relationships & comparisons are visual Less daunting to some than tables of numbers Allows some artistry and creativity Accuracy is important Style of graph must match Scale (level) of measurement of the variable(s) Nature of this particular data set Purpose of a Graph
Graphs for Discrete Data(counts) Data are in categories Nominal Ordinal (if few categories) Types of graph: Pie Chart Bar Chart or Pictograph (Excel: Column chart) Show the Frequency (count) or Percent
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Area of bars combined is 100% Area of each bar is proportional to its percent of total Bars do not touchbecause categoriesare discrete. Many variations; this is the most simple. BAR CHART: the Good
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PICTOGRAPH: the Good bars constructed of equal size simple icons
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PICTOGRAPH: the Ugly Elements of unequal size Just heads of some kids All children are playing except those from China – subtle racism
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BAR CHART – problems to consider:area, color – & why is that jogger there?
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Practice: How many problems can you see in this graph?
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PIE CHART: the Acceptable Area of pie = 100% Wedge is proportional to percentage of cases Labels show count or percent Ten slices is the maximum to remain clear & readable.
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PIE CHART: the Badcharts confuse or obscure the pattern in the data
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Graphs for Continuous Data (sometimes used for Ordinal data) Graph shows continuity of the construct Histogram: bars that touch at real limits Line graph: covers range (a.k.a. Frequency Polygon) Horizontal axis goes from low to high Intervals shown for Interval or Ratio data Some ordinal data also graphed this way(e.g., strongly agree, agree, slightly agree, etc)
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Bar width is a rangeof scores or the reallimits of scores. Ranges equal width Labels show mid-point or real limits Low scores on left, high scores on right HISTOGRAM: the Good
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HISTOGRAM: the Bad Ranges of data Unequal & indeterminate Spacing of “bars” is unequal. Water, sky, umbrella detract from graph
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Intervals of income are unequal/indeterminate.
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One interval is just plain wrong, and data are lost (all incomes $49,001 to $49,999 omitted).
Same requirements as histogram. If more than one line,legend or labels are needed. More than four or fivelines can be hard tointerpret Line Graphs / Frequency Polygon from SRB Documentary. (2008). Demographic Winter: the Decline of the Human Family at http://www.demographicwinter.com/index.html
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LINE GRAPH: the Bad Why is the headline “Steady growth” for this graph? Hint: check the axis values If it is growth, is it steady ? Hint: how did each of the three variables change from 1988 to 1989.
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Modern graphs have more options The Future of Food. (2008) WiredMagazine 16:11
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Chapter 2 and Infographics Project Graphs: Good, Bad & Ugly
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