The average time taken for your Internet service provider to remotely resolve a trouble ticket has a Normal distribution, with a mean of 4.3 hours and a standard deviation of 3.1 hours. What percentage of the tickets are resolved in less than half an hour?
A)11.0%
B)14.5%
C)85.5%
D)89.1%

Question

Quizplus · Accepted Answer

We need to find the percentage of tickets resolved in less than half an hour. 
Using the Z-score formula, 
Z = (X - μ) / σ
where X is the value we want to find the probability for, μ is the mean, and σ is the standard deviation. 
Plugging in the values, we get 
Z = (0.5 - 4.3) / 3.1 = -1.23 
Using a standard normal distribution table or calculator, we can find that the percentage of values to the left of Z = -1.23 is approximately 11.0%. Therefore, choice A is the best answer.

The Average Time Taken for Your Internet Service Provider to Remotely