Question

The advertised duration of the trip is 2 hours and 15 minutes. The company operating the ferry would like to increase its operational efficiency by reducing the standard deviation so that they are on time 95% of the time. How much do they have to reduce the standard deviation

Answer 1

The 2.88 minutes have to reduce the standard deviation to increase the efficiency.

According to the statement

we have given that the duration of the trip is 2 hours and 15 minutes. And we have to how much standard deviation be reduced to increase the operational efficiency.

So, For this purpose, we know that the

Let X be the time taken to reach the resort. Then it is  given that the

N (μ , σ).

Here μ is 2 hours then

μ  = 2*60 = 120 minutes.

And

Let σ be the reduced standard deviation such that new distributions becomes N (μ , σ)

Then P ( x <135)

here 135 is the minute format of 2 hours and 15 min.

So,

P ( x <135) = 0.95

And

P [ (x -120 / σ) < (135 -120 / σ)] = 0.95

P [ Z < ( 15 / σ)] = 0.95

And after solving it the

σ = 9.22 min.

i.e. 12 - 9.22 = 2.88 min.

So, The 2.88 minutes have to reduce the standard deviation to increase the efficiency.

Learn more about Standard deviation here

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Question:

The time it takes for a ferry to reach a summer resort from the mainland is Normally distributed with mean 2 hours and standard deviation 12 minutes. The advertised duration of the trip is 2 hours and 15 minutes. The company operating the ferry would like to increase its operational efficiency by reducing the standard deviation so that they are on time 95% of the time. How much do they have to reduce the standard deviation

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