Find the standard deviation - how do I plug in numbers to this formula

Question

The quiz scores are below.

 

5 3 9 10 9 9 10

10 10 9 6 4 9 9 

 

The formula is s =     Σ (x-^-x)²

                            √ -----------

                               (n-1)

 

The ^-x is X Bar aka the sample mean which I found is 8.

The square root sign above holds both the numerator and denominator if that was not clear

 

So I am a bit confused as to what to do next. The Σ of x is 112. n-1 is 13.

                              

                                

Answer 1

                   Quiz Scores                      X-Squared

                 ____________                  ___________

                         5                                     25

                         3                                       9

                         9                                      81

                        10                                   100

                          9                                    81

                          9                                    81

                         10                                  100                                            

                          10                                 100

                          10                                 100

                           9                                    81

                           6                                    36

                           4                                   16

                           9                                   81

                           9                                   81                           

                         ____                             _______

                    sum=112                          sum2= 972

 

n-1=13    X-Bar= 112 (sum)

                          ________

                             13           XBar= 8.62                   (x1 -x bar)  =(5-8.62)^2

                                                                                                   ____________

                                                                                                            13                   =13.10

 

 

 

 Sdiev= Sqrt(13.10)=3.62

 

                                                    Took a crack  at this problem .....