1) An outbreak of the deadly Ebola virus in 2002 and 2003 killed 91 of the 95 gorillas in seven home ranges in the Congo. To study the spread of the virus, researchers measure "distance" by the number of home ranges separating a group of gorillas from the first group infected.

Here are data on distance and number of days until deaths began in each later group: ( DATA IS IN PICTURE)

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