2.142 Worldwide airline fatalities Statistics published on www.

allcountries.org based on figures supplied by the U.S.

Census Bureau show that 24 fatal accidents or less were observed in 23.1% of years from 1987 to 1999, 25 or less in 38.5% of years, 26 or less in 46.2% of years, 27 or less in 61.5% of years, 28 or less in 69.2% of years, 29 or less in 92.3% of years from 1987 to 1999. These are called cumulative percentages.

a. What is the median number of fatal accidents observed in a year? Explain why.

b. Nearly all the numbers of fatal accidents occurring from 1987 to 1999 fall between 17 and 37. If the number of fatal accidents can be approximated by a bell-shaped curve, give a rough approximation for the standard deviation of the number of fatal accidents.

Explain your reasoning.