Customer satisfaction probability

Let the random variable ξ represent the number of satisfied customers. The probability of a satisfied customer for each of the four customers is 7/10. Specify:

a) probability distribution, distribution function F(x) and P(-0.5 < ξ < 3.1)
b) variance of the random variable ξ.

Final Answer:

p = ?
r =  0.84

Step-by-step explanation:

$$\begin{gathered} n=4 \\ q=7/10=\frac{7}{10}=0.7 \\ P(-0.5<\xi <3.1)=P(-0<\xi <3.1) \\ p=? \end{gathered}$$

$r=n\cdot q\cdot (1-q)=4\cdot 0.7\cdot (1-0.7)=0.84$

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