Question: Again use the worksheet Rollercoaster fall 08.MTW. It costs millions of dollars to build a rollercoaster. Typically the installation cost of a wooden rollercoaster is less than installation cost of a steel rollercoaster. Is the mean length of wooden rollercoasters greater than the mean length of steel rollercoasters?

a) Give a 98% confidence for the difference in the mean length of wooden rollercoasters and steel rollercoaster. Interpret this interval. (In Type column 1 = wood, 2 = steel.)

b) Test if the mean length of wooden rollercoasters is greater than the mean length of steel rollercoasters. Give the null and alternative hypothesis, p-value, decision of the test and conclusion. Use α =0.05.