Answer:
20
Step-by-step explanation:
Let X be the exponentially distributed random variable with the given mean E(X)=20
#To find the standard deviation, we first determine lambda,[tex]\lambda[/tex]:
[tex]20=E(X)=\frac{1}{\lambda}\\\\\\\lambda=\frac{1}{20}=0.05[/tex]
We then find standard deviation using the formula:
[tex]std(X)=\sqrt{\frac{1}{\lambda^2}}\\\\=\sqrt{\frac{1}{\0.05^2}}\\\\=20[/tex]
Hence, the standard deviation of the distance between two major cracks is 20
