4.9 The U.S. Department of Transportation reported the number of speeding-related crash fatalities for the 20 days of the year that had the highest number of these fatalities between 1994 and 2003 (Traffic Safety Facts, July 2005).

Date Speeding-Related Fatalities Date Speeding-Related Fatalities Jan 1 521 Aug 17 446 Jul 4 519 Dec 24 436 Aug 12 466 Aug 25 433 Nov 23 461 Sep 2 433 Jul 3 458 Aug 6 431 Dec 26 455 Aug 10 426 Aug 4 455 Sept 21 424 Aug 31 446 Jul 27 422 May 25 446 Sep 14 422 Dec 23 446 May 27 420

a. Compute the mean number of speeding-related fatalities for these 20 days.

b. Compute the median number of speeding-related fatalities for these 20 days.

c. Explain why it is not reasonable to generalize from this sample of 20 days to the other 345 days of the year.