States' Elevations

This exercise examines the distribution of the highest and lowest elevations in feet above (or below) sea level for the 50 states. Click on Data under Chapter 1 in the left panel and then select Open remote ... under the File menu in the right panel. Select elevations.xml from the Open File Dialog and click OK. Note that both Highest and Lowest elevations are assigned the Y role by default, whereas State is assigned the Label role. Select y|z from the Graph menu (conditioning z variables are not assigned here).

  1. Click on the histogram window displaying the Highest elevation variable to bring it to the front. Click on the right bar button until the each bar spans about 1000 feet. Characterize the resulting low and high elevation state groups regionally and the single outlier state.
  2. What state has the highest elevation in the low-elevation group (click on this state)? What is its elevation (examine the linked observation in the Elevations data set)?
  3. Would you characterize the Highest elevation distribution as symmetric, skewed to the right, skewed to the left, U-shaped, or uniform?
  4. Click on the histogram window for the Lowest elevation variable to bring it to the front. Click on the right bar button until the each bar spans about 250 feet. What states have their lowest elevations greater than 2500 feet? What are their elevations?
  5. What states have their lowest elevations below sea level? What are their elevations?
  6. Would you characterize the Lowest elevation distribution as symmetric, skewed to the right, skewed to the left, U-shaped, or uniform?
  7. The flatness of a state is the difference between its highest and lowest elevations. Select Transform... from the Column menu. Enter Highest - Lowest in the expression window and click OK. Double click on the new variable's heading. Rename the variable to Flatness and change its role to Y. Likewise, change the roles of Highest and Lowest variables to None by double clicking on their headings. What is Illinois' flatness value?
  8. What is the flattest state? What is its Flatness values?
  9. Guess the five flattest states. What are the five flattest states? What do they have in common? Do they include Kansas, Nebraska, Iowa, and Illinois?
  10. Why is the distribution of the Highest elevation variable similar to the distribution of the Flatness variable.