Answer:
The desviation is 8 4/7 or 8.571
Step-by-step explanation:
The conversion for any variable X to a standard z is
[tex]Z=\frac{X-\[Mu]}\\{\[Sigma]}[/tex]
where mu is the mean and sigma de desviation
You can find the value of Z whith the tables of the accumulated probability function. The accumulated probability for the mean is 0.5 .Remenber that the accumlated probability function represent the area at the left of an abscissa. Then
0.5+0.3531=0.8531
Acording to the accumulated probability function table, a Z=1.05 has an area of 0.8531 at its left.
Now it is only solving the equation
[tex]\[Sigma]=\frac{X-\[Mu]}{Z}[/tex]
σ=[tex]\frac{34-25}{1.05}[/tex]
σ=8.571
