a = different between frequencies of modal class and the class before it.
b= different between frequencies of modal class and the class after it.
c =class width of median class
Example: These numbers of books were read by each of the 28 students in a literature class. Find mean, median and mode.
Number of books
Frequency
0 – 2
2
3 – 5
6
6 – 8
12
9 – 11
5
12 – 14
3
Eighty randomly selected light bulbs were tested to determine their lifetimes (in hours). This frequency distribution was obtained. Find mean, median and mode.