Detailed Solutions to Practice #11

If you had difficulty with any part of this practice, read the detailed solution given below. When you are done reading the detailed solution, review this unit and try the additional practice.

Given the table below, construct a bar graph which displays the information.

1. Determine the following elements of the bar graph from the table
   • Title of the graph--The title of the graph is the same as the title of the table. This means the title of the graph will be: Annual Income of Four Employees
   • Label for each axis--The label for each axis comes from the column/row labels. In this table the data is placed in columns, so we will use the column labels.
     • Grouped Data Axis Label--This is the axis that contains the data groups. In this case it is the Employee.
     • Frequency Axis Label--This is the axis that contains the frequency counts. In this case it is the Income (in dollars).
       
   • Scale for each axis
     Determine the numerical scale for the frequency axis, then the group names for grouped data axis.
     • Grouped Data Axis Label--Employee
       This data contains four groups. The data is nominal (not ordered) so the groups could be placed in any order on the axis. The four groups on the scale are: (1) Sue, (2) Brian, (3) Dan, and (4) Nancy.
     • Frequency Axis Label--Income (thousands of dollars)
       The scale of the frequency axis is determined by the data. On this axis we must incorporate values which range from at least 25,000 to 38,000, the lowest and greatest incomes. The lowest value is 25,000 so it is not necessary to begin the scale at 0. If we begin the scale slightly below 25,000 and extend the scale slightly beyond 38,000 we have a scale which incorporates all values. One good choice for the scale is one which ranges from 20,000 to 40,000. Also, since all values are in the thousands we can incorporate this into the label of the axis, to make the label Income (thousands of dollars)
       
2. Draw a set of axes that you will use to construct your graph
   • Determine which axis will be the frequency axis--(Determine whether bars will go horizontally or vertically.) In this practice, we will place the frequency axis on the vertical axis. You could just as easily have chosen to place it on the horizontal axis

Write in axes labels--In the first step, we determined the axis label was Employee for the grouped data axis, in this case the horizontal axis. The frequency axis is labeled Income (thousands of dollars), and will be on the vertical axis. For the frequency axis, determine the scale interval--The scale of the frequency axis is from 20,000, or 20 thousand to 38,000, or 38 thousand. Since all the data points are in multiples of 1,000 we can start the scale at 20, and have the scale to 40 (thousands of dollars). The interval can be 2. This will make it easier to discern individual values.

3. Use the data from the table to draw in the bars on the graph.

   Once we have the axes drawn and labeled, we can draw in the bars. At the right is the bar graph that illustrates the data given in the table. Notice that the scale starts at 20 and goes to 40. We want the scale to go beyond the highest value. The scale doesn't start at zero since the values are compressed between 25 and 38. The interval for the graph is 2. This, along with a scale going from 20 to 40, makes it easier to determine individual data points. We can also clearly compare the data groups.

   
   

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