17-3 Standard Deviation and Variance

This weekend I am going to teach you all how problems that ask you for standard deviation and variance. Before I show you all an example of a problem like this, there are a few things that you need to know.
Notes:
• When you see the symbol, ∑ (sigma), it means the sum
• When you see xi, it is the numbers
• When you see n, it is how many numbers you have
• When you see x̅, it is the mean of the numbers
• The formula is: s^2 = ((∑(xi^2)) / (n)) - x̅ ^2
• When you are solving for standard deviation, you look for three things: n, x̅, and ∑(xi^2)
• You do this by setting up a chart with two columns; s and s^2
• The numbers are given to you in the problem
• After you find those three things, you just plug in and simplify
Example: Find the standard deviation of 5, 5, 7, 8, and 10
n= 5
x̅= 7
∑(xi^2)= 263

S= sq. root of ((263/5) – 49)
S= sq. root of (3.6)
S= 1.897

-Braxton