Volcanoes almost every year, there is some incidence of volcanic activity on the island of japan. in 2005 there were 5 volcanic episodes, defined as either eruptions or sizable seismic activity. suppose the mean number of episodes is 2.4 per year. let x be the number of episodes in the 2-year period 2010–2011. a) what model might you use to model x? b) what is the mean number of episodes in this period? c) what is the probability that there will be no episodes in this period? d) what is the probability that there are more than three episodes in this period?

An annual marathon covers a route that has a distance of approximately 26 miles. winning times for this marathon are all over 2 hours. the following data are the minutes over 2 hours for the winning male runners over two periods of 20 years each. earlier period 14 12 15 22 13 10 19 13 9 14 20 18 16 20 23 12 18 17 6 13 recent period 7 11 7 14 8 9 11 14 8 7 9 8 7 9 9 9 9 8 10 8 (a) make a stem-and-leaf display for the minutes over 2 hours of the winning times for the earlier period. use two lines per stem. (use the tens digit as the stem and the ones digit as the leaf. enter none in any unused answer blanks. for more details, view how to split a stem.) minutes beyond 2 hours earlier period 0 1 2 (b) make a stem-and-leaf display for the minutes over 2 hours of the winning times for the recent period. use two lines per stem. (use the tens digit as the stem and the ones digit as the leaf. enter none in any unused answer blanks.) minutes beyond 2 hours recent period (c) compare the two distributions. how many times under 15 minutes are in each distribution