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					Bar and Histograms (What Would You Use: Part 1)

Homework
                                   Histograms vs. Bar Graphs
Histograms and bar graphs look very similar and are used to compare data, but in different ways.
     With histograms, you have one variable, and sort data by this variable by placing them
        into "bins." The main question a histogram answers is: "How many measurements are
        there in each of the classes of measurements?"
     With bar graphs, you have several measurements of different items, and you compare
        them. The main question a bar graph answers is: "What is the measurement for each
        item?"

Below are some examples of comparisons you want to represent graphically. You need to choose
between using a bar graph or a histogram to represent the data. Which would you choose to use
in each case? Why?



           Situation                Bar Graph or                   Reasoning
                                    Histogram?
We want to compare the
total revenues of five different
companies.
We have measured revenues
of several companies. We
want to compare numbers of
companies that make from 0
to 10,000; from 10,000 to
20,000; from 20,000 to 30,000
and so on.
We want to compare heights
of ten oak trees in a city park
We have measured several
trees in a city park. We want to
compare numbers of trees that
are from 0 to 5 meters high;
from 5 to 10; from 10 to 15
and so on.


(Adapted from: http://www.ecu.edu/si/cd/interactivate/discussions/sd4.html)




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Sample Problems on Comparing Histograms and Bar Graphs

1. In the past year, you have recorded the number of tickets that a movie theater has sold during
each month. To represent this data set graphically, would you construct a bar graph or a
histogram? Why is this choice better than the other? Using the following data, construct the graph
that you choose.


                                                Number of
                                      Month
                                               Tickets Sold
                                       Jan.        25
                                       Feb.        30
                                      March        15
                                       April       20
                                       May         30
                                       June        35
                                       July        40
                                       Aug.        20
                                       Sept.       25
                                       Oct.        15
                                       Nov.        20
                                       Dec.        30




http://pulse.pharmacy.arizona.edu/math/what_would_you_use1.html
2. Over the past several years, you have recorded the number of automobiles that a used car
dealer in your town has sold in different price ranges. First, decide whether a histogram or a bar
graph is most appropriate for this situation.

Next, using the given data, construct several graphs of this situation using different intervals for
the price ranges (vary the increment size--$2,000 or $5,000, for example). If you were the car
dealer, what increment size would you choose to advertise car sales?


                                                      Number of
                                     Price Range
                                                      Cars Sold
                                       $0-$1,000           3
                                     $1,000-$1,999         5
                                     $2,000-$2,999         12
                                     $3,000-$3,999         25
                                     $4,000-$4,999         40
                                     $5,000-$5,999         75
                                     $6,000-$6,999         52
                                     $7,000-$7,999         35
                                     $8,000-$8,999         15
                                    $9,000-$10,000         9




(Source: http://www.ecu.edu/si/cd/interactivate/lessons/st5.html)




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