Class Interval Arithmetic Mean Definition:
     A range of values of a variable, an interval used in dividing the scale of the variable for the purpose of tabulating the frequency distribution of a sample. In other words, we can define as the individual group of scores in a grouped frequency distribution.

  Formula:

Class Interval Arithmetic Mean :
Arithmetic Mean = ΣfX/Σf
where
              X = Midpoint
              f = Frequency



Class Interval Arithmetic Mean Example: To find the Arithmetic Mean of

Intervals	Frequency(f)
10 - 20	3
20 - 30	9
30 - 40	5

  Step 1: Find Σf.
            Σf = 7

  Step 2: Then, Find the Midpoint for the class interval.
            Midpoint(X) = (10+20)/2, (20+30)/2, (30+40)/2 = 15, 25, 35
  Step 3: Now, Find ΣfX.

            ΣfX =((3*15)+(9*25)+(5*35)) = (45+225+175) = 445

Intervals	Frequency(f)	Midpoint	Xf
10 - 20	3	(10 + 20)/2 = 15	3 * 15 = 45
20 - 30	9	(20 + 30)/2 = 25	9 * 25 = 225
30 - 40	5	(30 + 40)/2 = 35	5 * 35 = 175

  Step 4: Now, Substitute in the above formula given.
            Arithmetic mean = ΣfX/Σf = 445/17 = 26.1765

This example will clearly illustrates how to calculate the Class Interval Arithmetic mean manually.