[EX03-006] Under the National Highway System Designation Act of 1995, states are allowed to set their own highway speed limits. Most of the states raised the limits. The 2005 maximum speed limits on interstate highways for cars and trucks by each state are given in the following table (in miles per hour).

State Cars Trucks State Cars Trucks State Cars Trucks AL 70 70 LA 70 70 OH 65 55 AK 65 65 ME 65 65 OK 75 75 AZ 75 75 MD 65 65 OR 65 65 AR 70 65 MA 65 65 PA 65 65 CA 70 55 MI 70 55 RI 65 65 CO 75 75 MN 70 70 SC 70 70 CT 65 65 MS 70 70 SD 75 75 DE 65 65 MO 70 70 TN 70 70 FL 70 70 MT 75 65 TX 75 75 GA 70 70 NE 75 75 UT 75 75 HI 55 55 NV 75 75 VT 65 65 ID 75 70 NH 65 65 VA 65 65 IL 65 55 NJ 65 65 WA 70 60 IN 65 60 NM 75 75 WV 70 70 IA 65 65 NY 65 65 WI 65 65 KS 70 70 NC 70 70 WY 75 75 KY 65 65 ND 75 75 Source: The National Motorists Association, http://www.motorists.com/issues/
speed/StateSpeeds.html

a. Build a cross-tabulation table of the two variables, vehicle type and maximum speed limit on an interstate highway. Express the results in frequencies, showing marginal totals.

b. Express the contingency table you derived in part a in percentages based on the grand total.

c. Draw a bar graph showing the results from part b.

d. Express the contingency table you derived in part a in percentages based on the marginal total for speed limit.

e. Draw a bar graph showing the results from part d.
FYI If you are using a computer or a calculator, try the cross-tabulation table commands on page 150.