what is the standard deviation for 9,5,9,5,9,5,9,5

Question

mathmale · Answer

Which methods are you currently using to find standard deviation?  By hand?  Using a simple calculator?  Using a calculator with statistics functions built in?  Knowing this will help me decide how to respond to your question.

anonymous · Answer

regular calculator

mathmale · Answer

do you have some paper and a pencil handy?  You'll need them.

anonymous · Answer

yes

mathmale · Answer

Add together these 8 numbers:  9,5,9,5,9,5,9,5.  Divide the sum by 8.  The result is the mean of your data set.  What is it?

anonymous · Answer

7

mathmale · Answer

Right.  Now I'm going to type in the formula for the standard deviation of a population:$$\sigma^2=\frac{ \sum_{1}^{n} (x-mean)^2}{ n }$$

mathmale · Answer

Have you seen this before?  Have you worked with it before?

mathmale · Answer

Note that you have already found the mean:  It is 7.