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Math Help - histogram of unequal class width

  1. #1
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    histogram of unequal class width

    for the class 100-199, the f (number of household) is 20, but in the histogram, the frequency is divided by 2 which 20/2 = 10 , but how can it show that in the class 100-199 , the total frequency of 100-199 is 10 ??? when look at the histogram, i would directly think that there are f=10 in the class of 100-199... how can it relate to the f for 100-199 is 20? i totally cant undrestand. histogram of unequal class width-img_20140616_064107-1-.jpghistogram of unequal class width-img_20140616_064133-1-.jpg
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    Re: histogram of unequal class width

    histogram is actually a plot of frequency DENSITY on y axis. to obtain the frequency, take the frequency density (the y-axis value), to multiply the width ( shown on the x-axis, for the 100-199 class it's 2). the area of each class represents the class's frequency, the y-value itself does not represent the frequency (unless the width of each class is the same)
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    Re: histogram of unequal class width

    Then why the book label the y axis as frequency ? Or the book is wrong?
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    Re: histogram of unequal class width

    No it's not wrong, it's just a bit sloppy. It would have been less ambiguous if they'd written "Frequency Density".
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