Investigation 15: Population Growths (due Wednesday, November 10)

You may work with one other person on this assignment, handing in one report with both names.  Word-processed reports are preferred to hand-written ones.  Please copy/paste Minitab output into a Word file as appropriate.

The following data are the percentage growths in population between 1990 and 2000 for each of the 50 states.  The states have been classified according to whether they are east or west of the Mississippi River.  The data can also be found in the Minitab worksheet PopulationGrowth.mtw.

States East of the Mississippi River:
Alabama 10.1, Connecticut 3.6, Delaware 17.6, Florida 23.5, Georgia 26.4, Illinois 8.6, Indiana 9.7, Kentucky 9.7, Maine 3.8, Maryland 10.8, Massachusetts 5.5, Michigan 6.9, Mississippi 10.5, New Hampshire 11.4, New Jersey 8.9, New York 5.5, North Carolina 21.4, Ohio 4.7, Pennsylvania 3.4, Rhode Island 4.5, South Carolina 15.1, Tennessee 16.7, Vermont 8.2, Virginia 14.4, West Virginia 0.8, Wisconsin 9.6

States West of the Mississippi River:
Alaska 14.0, Arizona 40.0, Arkansas 13.7, California 13.8, Colorado 30.6, Hawaii 9.3, Idaho 28.5, Iowa 5.4, Kansas 8.5, Louisiana 5.9, Minnesota 12.4, Missouri 9.3, Montana 12.9, Nebraska 8.4, Nevada 66.3, New Mexico 20.1, North Dakota 0.5, Oklahoma 9.7, Oregon 20.4, South Dakota 8.5, Texas 22.8, Utah 29.6, Washington 21.1, Wyoming 8.9

a) Create a side-by-side stemplot (stem-and-leaf display) of these data.  [Notes: Minitab does not produce this kind of graph.  A side-by-side stemplot puts the stems in a vertical column in the middle of the display.  It then puts leaves for one group to the right of the stem and leaves for the other group to the left.  The leaves are then ordered from the inside out (i.e., left-to-right for the group on the right side of the stems, and right-to-left for the group on the left side of the stems).  With these data it makes sense to put eastern states' leaves on the right and western states' leaves on the left.  It also makes sense to use the tens digit as the stem and the ones digit as the leaf, truncating the tenths digit.]

b) For each group of states (east and west), describe the shape of the distribution of its population growth percentages.

c) Calculate and report the five-number summary of the population growth percentages for each group of states.  [You may either do this by hand or with Minitab.]

d) Produce comparative boxplots of the population growth percentages for each group of states.  [You may either do this by hand or with Minitab.]

e) Show (by hand) the calculations involved in checking for outliers in both groups.  Also identify any outliers that you find.

f) Write a few sentences comparing and contrasting the population growth in states east vs. west of the Mississippi River, based on your graphical displays and numerical summaries.