The number of calls arriving at an interal switch board of an office i...
Solution:
Given that the number of calls arriving at an internal switch board of an office is 96 per hour.
We need to find the probability that there will be:
i) not more than 3 calls on the board
ii) at least 3 calls in a minute on the board given e‐¹.⁶ = 0.2019
To solve the above problem, we need to assume that the number of calls arriving at the switchboard follows a Poisson distribution. The Poisson distribution is given by:
P(X=k) = (e^-λ * λ^k)/k!
Where,
P(X=k) is the probability of getting k calls in a given time interval
e is the mathematical constant approximately equal to 2.71828
λ is the average rate of calls arriving at the switchboard
k is the number of calls
Let us assume that λ = 96/60 = 1.6 (since there are 60 minutes in an hour)
i) Probability of not more than 3 calls on the board
We need to find the probability of getting 0, 1, 2 or 3 calls on the board.
P(X ≤ 3) = P(X=0) + P(X=1) + P(X=2) + P(X=3)
= (e^-1.6 * 1.6^0)/0! + (e^-1.6 * 1.6^1)/1! + (e^-1.6 * 1.6^2)/2! + (e^-1.6 * 1.6^3)/3!
= 0.216 + 0.346 + 0.277 + 0.147
= 0.986
Therefore, the probability of not more than 3 calls on the board is 0.986.
ii) Probability of at least 3 calls in a minute on the board given e‐¹.⁶ = 0.2019
We need to find the probability of getting at least 3 calls in a minute, given e^-1.6 = 0.2019.
P(X ≥ 3) = 1 - P(X=0) - P(X=1) - P(X=2)
= 1 - (e^-1.6 * 1.6^0)/0! - (e^-1.6 * 1.6^1)/1! - (e^-1.6 * 1.6^2)/2!
= 1 - 0.2019 - 0.3231 - 0.2596
= 0.2154
Therefore, the probability of getting at least 3 calls in a minute on the board, given e^-1.6 = 0.2019, is 0.2154.
Hence, the solution is obtained.