# this is an exercise in arcgis mastering arcgis spacial analysis and modeling

Open the ex_6.mxd map document in the MapDocuments folder of the mgisdata directory and answer the following questions:ssouihjklgy;l;hgiur980-g4/

• (a) Recalculate the earthquake statistics without the missing data values and compare the results to the values reported in Figure 6.8. (b) Perhaps many quakes have missing magnitude values because they occurred before 1960, when seismic networks for measuring magnitudes were not yet common. Test this hypothesis and report what you find. (c) Examine the quake magnitudes on a map and propose an explanation for why the smaller quakes (magnitude less than 4) were included in the data set. (Hint: Use the query expression MAG > 0 AND MAG < 4.)
• How many counties in the United States have the name Washington? What is their total 2010 population? Which one has the largest area?
• Calculate the percentage of the population in each state that is African American. (Use the BLACK field for the African Americans and the POP2000 field for the total population in each state.) Which state has the largest number of African Americans? Which state has the largest percentage of African Americans?
• Which subregion of the country has the greatest number of African Americans? How many does it have?