The answer is (D.) Systematic desensitization
Systematic Desensitization is the behavioural technique used by Dr. Shakar which is used to treat anxiety disorders, fear, and phobias like Takeshi who is having a social phobia. The technique is to gradually exposed the person like Takeshi to an anxiety-producing object, event or place like when she is asked to walk on a busy street.
Do you speak english?..maybe i could help
Finding the new mean is simple: If ![E[X]=10](https://tex.z-dn.net/?f=E%5BX%5D%3D10)
, then ![E[2X]=2E[X]=20](https://tex.z-dn.net/?f=E%5B2X%5D%3D2E%5BX%5D%3D20)
.
Meanwhile, the standard deviation is the square root of the variance, which is given by
![V[X]=E[X^2]-E[X]^2\implies V[2X]=E[(2X)^2]-E[2X]^2=4E[X^2]-(2E[X])^2](https://tex.z-dn.net/?f=V%5BX%5D%3DE%5BX%5E2%5D-E%5BX%5D%5E2%5Cimplies%20V%5B2X%5D%3DE%5B%282X%29%5E2%5D-E%5B2X%5D%5E2%3D4E%5BX%5E2%5D-%282E%5BX%5D%29%5E2)
![\implies V[2X]=4\underbrace{\left(E[X^2]-E[X]^2\right)}_{V[X]}=12](https://tex.z-dn.net/?f=%5Cimplies%20V%5B2X%5D%3D4%5Cunderbrace%7B%5Cleft%28E%5BX%5E2%5D-E%5BX%5D%5E2%5Cright%29%7D_%7BV%5BX%5D%7D%3D12)
and so the new standard deviation would be ![\sqrt{V[2X]}=\sqrt{12}=2\sqrt3](https://tex.z-dn.net/?f=%5Csqrt%7BV%5B2X%5D%7D%3D%5Csqrt%7B12%7D%3D2%5Csqrt3)
.
