Mean from a frequency table
When data is in a table, multiply each value by its frequency, add these up, then divide by the total frequency.
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Analogy
Like finding the average of a stack of test scores where many students got the same mark.
Example
Total = 2 + 6 + 15 = 23Students = 2 + 3 + 5 = 10Mean = 23 / 10 = 2.3
In practice
Teachers use this to find the average score from a mark sheet.
Practice
Flashcards
- How do you find the mean from a frequency table?Multiply value by frequency, add up, divide by total frequency.
Questions people ask
Why do you multiply value by frequency?
Each value appears several times, so you count it that many times in the total. Three students scoring 2 add 3 x 2 = 6 to the sum. It saves writing out every single score. Then add all those products to get the grand total, and divide by the total frequency.
What is a common mistake with frequency tables?
Dividing by the number of rows instead of the total frequency. For the mean you divide by how many items there are in total, which is the sum of the frequency column. Not the number of values listed. Add a total row at the bottom of the frequency column to keep track of it.