Measures of Dispersion 2

Variance

- The average of the squared differences from the mean.

Standard Deviation

- Measurement of how spread out numbers are. Its is the square root of the variance.

There are two (2) types of formula for standard deviation :-
(1) Standard Deviation - Population             (2) Standard Deviation - Group

Standard Deviation (Population)    - Are always used for individual data.
Standard Deviation (Group)           - Always use the total frequency for finding variance.


Formula symbol keyword:






Steps to do the formula :-

1) Find the mean of the data/numbers
2) Subtract each number with the mean(from step 1) and square the answer
3) Find the mean of the answer(from step 2)
4) Square root the answer(from step 3) - Depends on the question requirement (Standard Deviation)

Example Question

Question = 1,4,14,1,14,1

Step 1
 Find the mean of the data/numbers



Step 2
Subtract each number with the mean(from step 1) and square the answer



Step 3
Find the mean of the answer(from step 2)



Step 4 
Square root the answer(from step 3) - ONLY CALCULATE WHEN THE QUESTION ASK! (Standard Deviation)



~Working Finish~