Statistics Studies !

[dufka]

Whats the difference between Midpoint and Upper End Points?? When are they used?

[Drake Glau]

Your upper end point is the upper end of your interval. Your midpoint if the middle point of the line. For simplicity's sake lets say you have f(x)=2 (straight horizontal line with 0 slope) where 2<=x<=4. You're upper end point is (4, 2) which is the point at the upper end of your interval. The midpoint would be (3, 2) since that would be right in the middle of line.

[ILM]

In statistics, especially when dealing with a big sample, it is easier to divide the sample for classes. For each class there is what is called an upper end points and midpoints.

1- Upper end points: when you have classes and there is a gap between the end of one class and the start of the other , then we take the upper end points (i am not sure i understand you will)

Here is a table that i did:

Years of experience Upper boundary

1-8 8.5

9-16 16.5

17-24 24.5

25-32 32.5

33-40 40.5

You can see the the first class end with 8 and the second start 9, so what if we have a value between 8 and 9 for this reason the use upper boundry, it seems stupid, but

2- Mid point: is the sum of the highest value and lowest value in a class divided by 2, it is the representative of that class. for example in class 1 (1-8) the mid point will be (8+1)/2 = 4.5

if you have any further consideration don't hesitate to ask.

[dufka]

Thank you both very much :*:* !!!

But I still dont understand

I know what is midpoint for! For example when there is a continous data and I need to find mean, then I have to find midpoint , I got it

But I dont know what is:

1) upper boundary and what is it need for ( is it the same as upper end point?)

2) Upper end point ?Is it necessary to construct cumulative fregeunecy graph??

3) Midpoints are needed to construct frequency polygon??

Please help me