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The time needed to complete a final examination in a particular college course is normally distributed with a mean of 80 minutes and a standard deviation of 10 minutes. Answer the following questions. (a) What is the probability of completing the exam in one hour or less?

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7 votes

Answer:

0.02275

Explanation:

We have been given that the time needed to complete a final examination in a particular college course is normally distributed with a mean of 80 minutes and a standard deviation of 10 minutes. We are asked to find the probability of completing the exam in one hour or less.

We know that 1 hour equals 60 minutes. First of all, we will find the z-score corresponding to 60 minutes.


z=(x-\mu)/(\sigma)

z = z-score,

x = Sample score,


\mu = Mean,


\sigma = Standard deviation.


z=(60-80)/(10)


z=(-20)/(10)


z=-2

Now, we will use normal distribution table to find area under z-score of
-2 as:


P(z< -2)


P(z< -2)=0.02275

Therefore, the probability of completing the exam in one hour or less is 0.02275.

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