MMMR From Frequency Tables

To understand how to calculate measures of central tendancy and spread of data sets presented in frequency tables

1. I can find the mean, median, mode and range of various data sets presented in frequency tables

2. I can add extra columns and rows to tables to help me analyse the data such as an 'fx' column and sum rows

Median: 2.5

Step 1: Add up the frequencies (in this case 14)

Step 2: Add 1 then divide by 2 (in this case 7.5)

Step 3: Because we got 7.5 we average the 7th and 8th score.

7th Score: 2

8th Score 3

Average: 2.5

Mean: 2.6

Step 1: Create an "fx" column which is

score x frequency

Step 2: Sum the fx's: (in this case 37)

Step 3: Divide the fx total by the frequency total

37/14 = 2.6

Mode: 37

Simple to find, it is the score with the highest frequency. In this case the class centre 37 has the highest frequency is 10

Range: 8

Highest score - lowest score.

In this case 37 - 29 = 8

Median: 35

Step 1: Add up the frequencies (in this case 31)

Step 2: Add 1 then divide by 2 (in this case 16)

Step 3: Because we got 16 we use the 16th class centre.

16th class centre: 35

Mean: 34.3

Step 1: Create an "fx" column which is

score x frequency

Step 2: Sum the fx's: (in this case 1063)

Step 3: Divide the fx total by the frequency total

1063/31 = 34.3