Question 6.378

33. Windy Frisco. The mean wind speed in San Francisco is 13.6 mph in July, according to the U.S. National Oceanic and Atmospheric Administration. Suppose that the distribution of the wind speed in July in San Francisco is normal with mean and standard deviation . Find the probability that a randomly chosen day in July has the following wind speeds:

  1. 7.2 mph or less
  2. Greater than 20 mph
  3. Between 15 and 20 mph
  4. Tours to Alcatraz Island are canceled if the day is too windy, specifically if the wind speed is higher than 99% of all other wind speeds in July. Find the cutoff wind speed.
  5. Suppose that a particular day in July has no wind at all. Should this be considered unusual? On what do you base your answer?

6.5.33

(a) 0.1423 (b) 0.1423 (c) 26.67% (d) (e) -score is −2.27; moderately unusual