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I got 45 for the range but I can't figure out the variance or standard deviation. Please help and show work so I can understand how to do this. Thanks.

 Jan 9, 2020
 #1
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Find the average  =  [ 35 + 50 + 60 + 60 + 75 + 65 + 80 ]  / 7  =  425 / 7

 

Take  each  value and subtract it from the  average, then......square these differences

 

So we have

                       diff                  square

425/7 - 35   = 180/7     ⇒      32400/49      

425/7 - 50  =  75/7   ⇒          5625/49

425/7 - 60  =  5/7    ⇒           25/49

425/7 - 60  = 5/7    ⇒            25/49

425/7 - 75  = - (100/7)   ⇒    10000/49

425/7 - 65  =  -(30/7)    ⇒      900/49

425/7 - 80 = - (135/7)   ⇒     18225/49

 

Take the average  of the  last column  =

 

[ 32400 + 5625 + 25 + 25 + 10000 + 900 + 18225) / 49  / 7 =  9600 / 49  this is the variance

 

The square root of this is the standard deviation   = √[9600/49]  ≈   14

 

 

cool cool cool

 Jan 9, 2020

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