# calculation of probability with normal distribution.

Is lack of sleep causing traffic fatalities? A study conducted under the auspices of the National Highway Traffic Safety Administration found that the average number of fatal crashes caused by drowsy drivers each year was 1550 (Business Week, January 26, 2004). Assume the annual number of fatal crashes per year is normally distributed with a standard deviation of 300.

a. Determine the probability of fewer than 1000 fatal crashes in a year.

b. Determine the probability the number of fatal crashes will be between 1000 and 2000 for a year.

c. For a year to be in the upper 5% with respect to the number of fatal crashes, determine how many fatal crashes would have to occur.

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#### Solution Summary

The solution is comprised of the detailed explanations of calculations of probability under normal distribution. It provides step-by-step calculations.