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Homework Help: Statistics - Probability & z-score

  1. Jul 27, 2010 #1
    The average amount of time people spend on facebook each day is 64 minutes, with a standard deviation of 4.5 minutes. Are you more likely to select a random person that spends less than 62 minutes per day, or a group of 35 people that spend on average less than 62 minutes per day on facebook? How many minutes would a person have to be on facebook to be considered the top 5%?

    Z= X - M / SD

    I am pretty sure this is the formula to use for this problem. I just got confused with what the number of people would be for the first half of the problem, the random person, because it is not given. If anyone can point me in the right direction it would be greatly appreciated. Thank you very much.
  2. jcsd
  3. Jul 27, 2010 #2
    You are comparing two experiments. One has 35 people in it. How many does the other have in it?
  4. Jul 28, 2010 #3
    That lies the problem. What is written is all that is given for the problem and that is also why I am having such difficulty.
  5. Jul 28, 2010 #4
    If you pick 35 random people out of the population, the size of your sample is 35.
    If you pick one random person out of the population, the size of your sample is... one.
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