# Thread: histogram of unequal class width

1. ## 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.

2. ## 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)

3. ## Re: histogram of unequal class width

Then why the book label the y axis as frequency ? Or the book is wrong?

4. ## 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".