Respuesta :
Answer:
The probability that a randomly selected group of four trees can be used as timber is 4.5 × 10⁻⁵
Step-by-step explanation:
The given parameters are;
Mean = 34 cm
The standard deviation = 8 cm
The mean
The Z score is [tex]Z=\dfrac{x-\mu }{\sigma }[/tex], which gives;
For x = 30 we have;
[tex]Z=\dfrac{30-34 }{8 } = -0.5[/tex]
P(x>30) = 1 - 0.30854 = 0.69146
For x = 40, we have
[tex]Z=\dfrac{40-34 }{8 } = 0.75[/tex]
P(x < 40) = 0.77337
Therefore, the probability that the mean of four trees is between 30 and 40 is given as follows;
P(30 < x < 40) = 0.77337 - 0.69146 = 0.08191
The probability that a randomly selected group of four trees can be used as timber is given as follows;
Binomial distribution
[tex]P(X = 4) = \dbinom{4}{4} \left (0.08191\right )^{4}\left (1-0.08191 \right )^{0} = 4.5 \times 10^{-5}[/tex]
