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  1. It is stated that 86% of U.S. respondents use a cell phone exclusively for their telephone service. In a sample of twelve households,
    1. Find the probability that fewer than 6respondents use a cell phone as their exclusive telephone service.
    2. Find the probability that exactly 11respondents exclusively use a cell phone for telephone service.
  2. Clients facing trouble with their Internet may call a number for support. The time it takes the technician to resolve the problem is equally likely to be between 30 seconds and 8 minutes.
    1. What are the values for a and b in minutes?

What is the mean time to resolve the problem? What is the standard deviation of the time?

What percent of the problems take more than 7 minutes to resolve?

Suppose we wish to find the middle 80% of the problem-solving times. What are the end points of these two times?

  1. Google stock was trading for an average of $1018.27 on 2/9/2018. Suppose the value of the stock that day was normally distributed with a standard deviation of $8.57.
  2. What was the probability that the stock was valued between $1020 and $1060?

Five percent of the time the stock was trading at what value or higher?

What is the maximum price you should pay if you don’t want to exceed the twentieth percentile of costs?

  1. A study found the average song in the top 100 on iTunes is 226.93 seconds with a standard deviation of 31.50 seconds.
  2. What is the probability that a randomly selected song is less than two and a half minutes?
  3. What percent of songs are longer than the Beatles’ Revolution (3 minutes 21 seconds)?
  4. In a sample of 16 songs, what is the likelihood that the mean song length is longer than 4 minutes?
  5. In repeated samples of 16 songs, we’d expect 95% of mean song lengths to be between what two numbers?