Every year hundreds of thousands of northern fur seals return to their haul-outs

Question

Every year hundreds of thousands of northern fur seals return to their haul-outs in a certain island in Alaska to breed, give birth, and teach their pups to swim, hunt, and survive in the Bering Sea. U.S. commercial fur sealing operations continued until 1984, but despite a reduction in harvest, the population of fur seals has continued to decline. Possible reasons include climate shifts in the North Pacific, changes in the availability of prey, and new or increased interaction with commercial fisheries that increase mortality. Suppose the following are data on the number of fur seal pups born on the island (in thousands) from 1979 to 2012, where a dash indicates a year in which no data were collected.

a) Make a stemplot to display the distribution of pups born per year. (Round down to the next whole number. Enter numbers from smallest to largest separated by spaces. Enter NONE for stems with no values.)

b) Describe the variability of the distribution. (Round your answers to whole numbers.)

The variability of the distribution is from _________ thousand pups to _________ thousand pups.

Pups born Pups born Year (thousands) Year (thousands) 170.12 1979 245.93 1996 1997 1980 203.82 179.44 179.15 1981 1998 203.58 1982 1999 158.74 1983 165.94 2000 174.27 1984 200 145.72 985 182.26 2002 1986 167.66 2003 1987 122.82 171.61 2004 1988 202.23 2005 171.53 109.96 989 2006 201.30 2007 1990 102.67 1991 2008 1992 182.44 2009 94.50 1993 2010 2011 1994 192.1 2012 1995 96.83

Explanation / Answer

(a)

Following table show sthe rounded data:

Following is the stem and leaf display of the data:

(b)

The variability shows the spread of the distribution.

The variability of the distribution is from 95 thousands pups pups to 246 thousand pups.

Pups Born Rounded data 245.93 246 203.82 204 179.44 179 203.58 204 165.94 166 174.27 174 182.26 182 167.66 168 171.61 172 202.23 202 171.53 172 201.3 201 182.44 182 192.1 192 170.12 170 179.15 179 158.74 159 145.72 146 122.82 123 109.96 110 102.67 103 94.5 95 96.83 97

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