Ski Patrol: Avalanches Snow avalanches can be a real problem for travelers in the western United States and Canada. A very common type of avalanche is called the slab avalanche. These have been studied extensively by David McClung, a professor of civil engineering at the University of British Columbia. Slab avalanches studied in Canada have an average thickness of m 5 67 cm (Source: Avalanche Handbook by D. McClung and P. Schaerer).

The ski patrol at Vail, Colorado, is studying slab avalanches in its region. A random sample of avalanches in spring gave the following thicknesses (in cm):

59 51 76 38 65 54 49 62 68 55 64 67 63 74 65 79 i. Use a calculator with mean and standard deviation keys to verify that x < 61.8 and s < 10.6 cm.

ii. Assume the slab thickness has an approximately normal distribution. Use a 1% level of signifi cance to test the claim that the mean slab thickness in the Vail region is different from that in Canada.