SOLUTION: The mean of numbers 3,6,4,x and 7 is 15.find the standard deviation

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Question 1152846: The mean of numbers 3,6,4,x and 7 is 15.find the standard deviation
Found 2 solutions by MathLover1, MathTherapy:
Answer by MathLover1(20850) About Me  (Show Source):
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The mean of numbers 3,6,4,x and 7+is 15.
find the standard deviation
first find x

%283%2B6%2B4%2Bx%2B7+%29%2F5+=15
20%2Bx+=15%2A5
x+=75-20
x+=55
the standard deviation:
3,6,4,55,7+
Then, take each number, subtract the mean and square the result:
%283-15%29%5E2=144
%286-15%29%5E2=81
%284-15%29%5E2=121
%2855-15%29%5E2=1600
%287-15%29%5E2=64
---------------------------------
sum of Differences^2------=144%2B81%2B121%2B1600%2B64=2010
find Variance: Sum of Differences^2 / (Count−1)
Variance=2010%2F4=502.5
Standard Deviation: the square root of the variance
delta=sqrt%28502.5%29≈22.4165

Answer by MathTherapy(10557) About Me  (Show Source):
You can put this solution on YOUR website!
The mean of numbers 3,6,4,x and 7 is 15.find the standard deviation
If these numbers represent a POPULATION - and I believe they do - then the correct answer is: highlight_green%28matrix%281%2C4%2C+Standard%2C+deviation%2C+%22is%3A%22%2C+20.05%29%29

If they represent a SAMPLE distribution, then it's a different answer.