Answer:
a) 0.9
b) Mean = 1.58
Standard Deviation = 0.89
Explanation:
We are given the following in the question:
A marketing firm is considering making up to three new hires.
Let X be the variable describing the number of hiring in the company.
Thus, x can take values 0,1 ,2 and 3.

a) P(firm will make at least one hire)

Also,


b) expected value and the standard deviation of the number of hires.
![E(x^2) = \displaystyle\sum x_i^2P(x_i)\\=0(0.1) + 1(0.4) + 4(0.32) +9(0.18) = 3.3\\V(x) = E(x^2)-[E(x)]^2 = 3.3-(1.58)^2 = 0.80\\\text{Standard Deviation} = √(V(x)) = √(0.8036) = 0.89](https://img.qammunity.org/2021/formulas/mathematics/college/mk2chdzehavjw7ihnzntqbifh1hh4rkpeo.png)