Normal Distribution Probability

MathematicsNormal DistributionMedium

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A lawyer commutes daily from his suburban home to his midtown office. On the average the trip one way takes 24 minutes, with a standard deviation of 3.8 minutes. Assume the distribution of trip times to be normally distributed. What is the probability that a trip will take at least 1/2 hour?

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Step by Step Written Solution

1
Step 1

In this problem, we are looking at a lawyer's commute time, which follows a normal distribution. We want to find the probability that a single trip takes at least half an hour.

Normal Distribution Problem

2
Step 2

First, let's identify the given values from the text. The average trip time, or the mean, is twenty-four minutes.

$$\mu = 24\text{ min}$$
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Step 3

Next, the standard deviation is given as three point eight minutes.

$$\sigma = 3.8\text{ min}$$
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Step 4

The question asks for the probability that a trip takes at least half an hour. Since our other values are in minutes, let's convert one half hour to thirty minutes.

$$x \ge 30\text{ min}$$
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Step 5

To find this probability, we first need to convert our value of thirty minutes into a standard z-score.

1. Calculate the Z-score

$$z = \frac{x - \mu}{\sigma}$$
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Step 6

Plugging in our values, we have thirty minus twenty-four in the numerator, divided by three point eight.

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Step 7

Subtracting twenty-four from thirty gives us six.

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About This Question

Subject
Mathematics
Topic
Normal Distribution
Difficulty
Medium
Question Type
Open Ended

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