
Chapter 3
76
Example 3.3
From Table 3.6, nd the arithmetic mean.
TABLE 3.6
Data related to class intervals and frequencies
Class interval Frequencies
0–10 5
10–20 7
20–30 19
30–40 12
40–50 5
50–60 2
60–70 7
Solution: For computing arithmetic mean in a continuous frequency distribution, we need to
compute the midpoint of class intervals (x). The midpoints are multiplied by the corresponding
frequencies (fx). The sum of this product is obtained and is divided by the sum of frequencies
(Table3.7).
TABLE 3.7
Data given in Table 3.6 arranged with class midpoint, frequencies, and the product of mid-points
and frequencies
Size Midpoint (x) Frequencies (f) fx
0–10 ...