Hey guys, I need help with this.

Discussion in 'General' started by Fluency, Dec 1, 2011.

  1. I'm terrible at math. I always have been. None of it makes sense to me, and I've struggled in every math class I've ever been in. I'm taking statistics in college and the class is really hard for me. I don't have a graphing calculator and I barely understand the material (not nearly enough to take this quiz). I have a 57 in the class right now, and there's only going to be two more grades this semester.

    The professor was dumb enough to give us a 6 question take home quiz, but I can't even find enough help on google. I understand this is a long shot, but if anyone could do out any of the problems I would appreciate it very much. Thanks in advance.

    1. The operating life of an Arctic Air portable cooler is normally distributed with mean 75 months and standard deviation 9 months. The manufacturer will replace any cooler that breaks during the guarantee period.
    a. If the guarantee period is for 64 months, what fraction of the coolers will the manufacturer have to replace?
    b. How long should the guarantee run if the manufacturer does not want to replace more than 2.5% of the coolers?

    2. Researchers at a pharmaceutical company have found that the effective time duration of a safe dosage of a pain relief drug is normally distributed with mean 2 hours and standard deviation 0.3 hours. For a patient selected at random:
    a. What is the probability that the drug will be effective for 2 hours or less?
    b. What is the probability that the drug will be effective for 1 hour or less?
    c. What is the probability that the drug will be effective for 3 hours or more?

    3. Coast Guard inspectors have found that 16% of all lifeboats on large cruise ships have a faulty latch release. A large cruise ship has 73 lifeboats. What is the probability that 9 or more of the lifeboats have a faulty latch release?

    4. The life of one species of poplar tree is normally distributed with mean 20 years and standard deviation 2.3 years.
    a. If one tree is selected at random, what is the probability that it will live 21 years or more?
    b. If nine trees are selected at random, what is the probability that the sample mean life of the nine trees will be 21 years or more?
    c. Can we assume that the sample means follow a normal distribution? Explain

    5. The body temperature of healthy children is normally distributed with
    mean 98.6 and standard deviation 0.9 .
    a. If one healthy child is chosen at random, what is the probability that
    the body temperature is more than 99.6 ?
    b. If 25 healthy children are chosen at random what is the probability
    that the sample mean body temperature ̅ is more than 99.6 ?

    6. Hank has a hot dog stand across the street from a little league ball field. He
    has observed that the daily demand for hot dogs on a weekend follows a
    normal distribution with mean μ = 400 and standard deviation σ = 50.
    a. Find the probability that the demand for hot dogs on a weekend day
    chosen at random will be less than 300
    b. Find the probability that the sample mean demand for a random
    sample of 4 weekend days will be less than 300
    c. Compare your answers to parts a and b. Explain the difference
     
  2. I really like math, but I also am terrible at it. Wish I could help :/
     
  3. Yeah, I do like math and how easily it can be used to figure out certain things, I just hate how hard it is for me.

    Thanks for the thought though, man.
     
  4. this is such a shitty situation
     

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