Answer:
a) 0.4452
b) 0.0548
c) 0.0501
d) 0.9145
e) 6.08 minutes or greater
Step-by-step explanation:
We are given the following information in the question:
Mean, μ = 4.7 minutes
Standard Deviation, σ = 0.50 minutes.
We are given that the distribution of length of the calls is a bell shaped distribution that is a normal distribution.
Formula:
![z_{score} = \displaystyle\frac{x-\mu}{\sigma}](https://tex.z-dn.net/?f=z_%7Bscore%7D%20%3D%20%5Cdisplaystyle%5Cfrac%7Bx-%5Cmu%7D%7B%5Csigma%7D)
a) P(calls last between 4.7 and 5.5 minutes)
![P(4.7 \leq x \leq 5.5) = 44.52\%](https://tex.z-dn.net/?f=P%284.7%20%5Cleq%20x%20%5Cleq%205.5%29%20%3D%2044.52%5C%25)
b) P(calls last more than 5.5 minutes)
Calculating the value from the standard normal table we have,
![1 - 0.9452 = 0.0548 = 5.48\%\\P( x > 5.5) = 5.48\%](https://tex.z-dn.net/?f=1%20-%200.9452%20%3D%200.0548%20%3D%205.48%5C%25%5C%5CP%28%20x%20%3E%205.5%29%20%3D%205.48%5C%25)
c) P( calls last between 5.5 and 6 minutes)
![P(5.5 \leq x \leq 6) = 5.01\%](https://tex.z-dn.net/?f=P%285.5%20%5Cleq%20x%20%5Cleq%206%29%20%3D%205.01%5C%25)
d) P( calls last between 4 and 6 minutes)
![P(4 \leq x \leq 6) = 91.45\%](https://tex.z-dn.net/?f=P%284%20%5Cleq%20x%20%5Cleq%206%29%20%3D%2091.45%5C%25)
e) We have to find the value of x such that the probability is 0.03.
P(X > x)
Calculation the value from standard normal z table, we have,
P(z < 2.75) = 0.997
Hence, the call lengths must be 6.08 minutes or greater for them to lie in the highest 3%.