Post on 30-Jun-2015
description
Review of Bar Graphs
ObjectivesAfter completing this unit you should be able to:
● Identify the bar graph title.● Identify labels for the bar graph axes.● Identify information given by a designated bar● Make statements about data trends from a bar graph.
What is a Bar Graph?A bar graph is a visual display used to compare the amounts or frequency of occurrence ofdifferent characteristics of data. This type of display allows us to:
● compare groups of data, and to● make generalizations about the data quickly.● to organize data and information of the amount of things or people.● it is a survey to collect data from different characteristics.
This unit will introduce basic bargraphs, how to read bar graphs. Anexample of a bar graph is given onthe right.When reading a bar graph there areseveral things we must pay attentionto: the graph title, two axes,including axes labels and scale, andthe bars. Since bar graphs are usedto graph frequencies or amounts ofdata in discrete groups, we willneed to determine which axis is thegrouped data axis, as well as whatthe specific groups are, and whichis the frequency axis.
Price of Corn versus Quantity Demanded
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Graph title, scale, labels,bars,axes. Group data axis, frequency,discrete.
The height of the bars are particularly important since they give us information about specificdata.
Parts of a Bar GraphNow let's look at the components of a bar graph individually. There is a lot of information inthis section so you may wish to jot down some short notes to yourself.
● Graph TitleThe graph title givesan overview of the informationbeing presented in the graph. Thetitle is given at the top of the graph.
● Axes and their labelsEachgraph has two axes. The axeslabels tell us what information ispresented on each axis. One axisrepresents data groups, the otherrepresents the amounts orfrequency of data groups.
● Grouped Data AxisThegrouped data axis is always at thebase of the bars. This axisdisplays the type of data beinggraphed.
● Frequency Data AxisThe frequency axis has a scale that is a measure of thefrequency or amounts of the different data groups.
● Axes Scale Scale is the range of values being presented along the frequency axis.● BarsThe bars are rectangular blocks that can have their base at either vertical axis
or horizontal axis (as in this example). Each bar represents the data for one of the datagroups.
Now let's look more closely at how the elements of a bar graph help us get a handle on theinformation presented in a graph. While there are several ways to do this, here we willpresent one way to get an overview of a graph using the graph above.
● Graph Titleprovides an overview of the type of information given in the bar graph.● For the bar graph given, the title indicates that we are looking at data on:● Vertical axisThis axis is the frequency axis and contains the quantity demanded
given in units of bushels.● Grouped Data AxisSince the the grouped data axis is always at the base of the
bars, the grouped data axis is the horizontal axis. The axis label tells us that along the
horizontal grouped data axis we have the price per bushel, with each data group beinga different dollar amount from $1 to $5.
● Two important pieces of information we must determine are the:○ type of data being counted, and○ how the data is grouped.
● Frequency Data AxisThe scale is the range of frequency values shown on thegraph. The span of values represented is determined by the lowest and greatestvalues you wish to include on the graph.
● When lookingat this axis,look to seewhere therange beginsand ends, aswell as at theintervalbetween tickmarks. For afurtherdiscussion onscale, readthe section on
Scale.● The vertical
axis is thequantitydemandedgiven in unitsof bushels.
● In this case,the frequencyscale goesfrom 0 to 80,and uses aninterval ofunits of 10.The frequencyof our datagroups range
●
over nearlythe entirescale so weare able toget a goodpicture of ourdata.
Example
Given the graph at right, below, answer the following questions
1.