Introduction
Let’s start off with some raw data (not a grouped frequency) .
Example: Alex did a survey of how many games each of 20 friends owned, and got this:
9, 15, 11, 12, 3, 5, 10, 20, 14, 6, 8, 8, 12, 12, 18, 15, 6, 9, 18, 11
To find the Mean, add up all the numbers, then divide by how many numbers there are:
Mean = 9+15+11+12+3+5+10+20+14+6+8+8+12+12+18+15+6+9+18+11/20 = 11.1
To find the Median, place the numbers in value order and find the middle number (or the mean of the middle two numbers). In this case the mean of the 10th and 11th values:
3, 5, 6, 6, 8, 8, 9, 9, 10, 11, 11, 12, 12, 12, 14, 15, 15, 18, 18, 20:
12 appears three times, more often than the other values, so Mode = 12
Grouped Frequency Table
Now, let’s make a Grouped Frequency Table of Alex’s data:
Number of games Frequency
1-5 2
6-10 7
11-15 8
16-15 3
(It says that 2 of Alex’s friends own somewhere between 1 and 5 games, 7 own between 6 and 10 games, etc)
Estimating the Mean from Grouped Data
So all we have left is:
Read more below-
SS1 Mathematics Third Term: Calculation of Mean, Median, Mode of Grouped Data
