Class Width's in Statistics.

[Alchemist4lyf]

Alright. Now, im facing this problem. The concept of class widths is needed for obtaining the histograms, where the class widths differ and we have to use frequency density.
But, i'm having trouble realizing what the class width is.
In some places it says, its the difference between the class boundaries of the class. The boundaries of the class are, the lower limit - 0.5, making the lower class boundary. And the upper boundary is the upper limit + 0.5. The difference of this gives us the class width.
However, in some places, it is said that the class width is actually the difference between the upper class limit and lower class limit of the same class.
In another place, it says, it's the difference between the upper class limits, or the lower class limits, of different classes.

So, please XPF, could you clear this problem, as soon as possible. All help will be appreciated.

 

[SalmanPakRocks]

Alright. Now, im facing this problem. The concept of class widths is needed for obtaining the histograms, where the class widths differ and we have to use frequency density.
But, i'm having trouble realizing what the class width is.
In some places it says, its the difference between the class boundaries of the class. The boundaries of the class are, the lower limit - 0.5, making the lower class boundary. And the upper boundary is the upper limit + 0.5. The difference of this gives us the class width.
However, in some places, it is said that the class width is actually the difference between the upper class limit and lower class limit of the same class.
In another place, it says, it's the difference between the upper class limits, or the lower class limits, of different classes.

So, please XPF, could you clear this problem, as soon as possible. All help will be appreciated.

Simple if u want to construct a Histrogram then u will need 3 things
Class Boundary
Frequency
Class Widht (If Class Intervals are given then u also have to calculate class boundary)
Class Width=Difference between Upper class BOUNDARY and Lower CLASS BOUNDARY !!
if Class Width is not equal then Frequency Density is calculated and it is = frequency/Class Width
hopes this clears up

 

[Alchemist4lyf]

Yar. Laikin they say, class boundary is this. Lower class boundary = lower class limit - 0.5. Upper class boundary = upper class limit + 0.5. In that case, i get an answer, that is 1 unit greater than the ones given in the book. And i'm quite certain they take class widths to be the difference between class LIMITS, of the same class. :S

 

[abcde]

Class boundaries are usually used to construct frequency polygons. For histograms with varying class widths, you use the second definition of class width i.e.
Class width = upper class limit - lower class limit
For instance, if the class interval is 70-75 cm and the frequency is 10:
=> Class width = 75 - 70 = 5 cm
=> Frequency density = frequency/ class width
= 10/5
= 2.

 

[Alchemist4lyf]

Oo thank you abcde... really, like, thanks a lot. You da man..

 

[abcde]

You're welcome!

 

[SalmanPakRocks]

Class boundaries are usually used to construct frequency polygons. For histograms with varying class widths, you use the second definition of class width i.e.
Class width = upper class limit - lower class limit
For instance, if the class interval is 70-75 cm and the frequency is 10:
=> Class width = 75 - 70 = 5 cm
=> Frequency density = frequency/ class width
= 10/5
= 2.

Now I m confused :%) :%)
I saw a question and in the table CLASS BOUNDARY Was given
e.g
10-15
15-20
20-25
Now the Class width for these is 5 so this way we are taking Class Boundary for Class Width !! :crazy:

 

[abcde]

I think whether you take class boundary or class limit is case dependent. There isn't a single 'hard-and-fast' definition. Use your good judgement. Whatever word is used, the class width would simply be the difference between the upper and lower class limits/boundaries of a specific class interval.