The Normal and Lognormal Distributions John Norstad j-norstad@northwestern.edu http://www.norstad.org February 2‚ 1999 Updated: November 3‚ 2011 Abstract The basic properties of the normal and lognormal distributions‚ with full proofs. We assume familiarity with elementary probability theory and with college-level calculus. 1 1 DEFINITIONS AND SUMMARY OF THE PROPOSITIONS 1 Definitions and Summary of the Propositions ∞ √ Proposition 1: −∞ 2 2 1 e−(x−µ) /2σ
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Weston Materials‚ Inc.‚ a national manufacturer of unattached garages‚ reports that it takes two construction workers a mean of 32 hours and a standard deviation of 2 hours to erect the Red Barn model. Assume the assembly times follow the normal distribution. a. Determine the z values for 29 and 34 hours. What percent of the garages take between 32 hours and 34 hours to erect? z(29) = (29-32)/2 = -3/2 z(34) = (34-32)/2 = 1 z(32) = 0 P(32 < x < 34) = P(0< z < 1) = 0.34 b. What percent of the
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X-bar Definition 1 x xi n i 1 Probability and statistics - Karol Flisikowski n Sampling Distribution of x-bar How does x-bar behave? To study the behavior‚ imagine taking many random samples of size n‚ and computing an x-bar for each of the samples. Then we plot this set of x-bars with a histogram. Probability and statistics - Karol Flisikowski Sampling Distribution of x-bar Probability and statistics - Karol Flisikowski Central Limit Theorem The key to the
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Probability Distribution Essay Example Suppose you flip a coin two times. This simple statistical experiment can have four possible outcomes: HH‚ HT‚ TH‚ and TT. Now‚ let the random variable X represent the number of Heads that result from this experiment. The random variable X can only take on the values 0‚ 1‚ or 2‚ so it is a discrete random variable Binomial Probability Function: it is a discrete distribution. The distribution is done when the results are not ranged along a wide range‚ but are
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AMA470 Midterm exam March 5‚ 2010 Please show full working out in order to obtain full marks. 1. Suppose that: • The number of claims per exposure period follows a Poisson distribution with mean λ = 110. • The size of each claim follows a lognormal distribution with parameters µ and σ 2 = 4. • The number of claims and claim sizes are independent. (a) Give two conditions for full credibility that can be completely determined by the information above. Make sure to define all terms in your definition
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skewed-right distribution with a mean of 10 minutes and a standard deviation of 8 minutes. Suppose 100 flights have been randomly sampled. Describe the sampling distribution of the mean waiting time between when the airplane taxis away from the terminal until the flight takes off for these 100 flights. a) Distribution is skewed-right with mean = 10 minutes and standard error = 0.8 minutes. b) Distribution is skewed-right with mean = 10 minutes and standard error = 8 minutes. c) Distribution is approximately
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of this course will provide students with a working knowledge of the principles of statistics‚ the ability to analyze and solve problems involving probability‚ and a working knowledge of averages and variations‚ normal probability distributions‚ sampling distributions‚ confidence intervals and testing statistical hypotheses. The emphasis of the course will be on the proper use of statistical techniques and their implementation rather than on mathematical proofs. (Prerequisite: MATH110 formerly MA112)
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The Poisson probability distribution‚ named after the French mathematician Siméon-Denis. Poisson is another important probability distribution of a discrete random variable that has a large number of applications. Suppose a washing machine in a Laundromat breaks down an average of three times a month. We may want to find the probability of exactly two breakdowns during the next month. This is an example of a Poisson probability distribution problem. Each breakdown is called an occurrence in Poisson
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(10 points) 3. Suppose that a random sample of size 64 is to be selected from a population having [pic] and standard deviation 5. (a) What are the mean and standard deviation of the [pic] sampling distribution? Can we say that the shape of the distribution is approximately normal? Why or why not? (10 points) (b) What is the probability that [pic] will be within 0.5 of the population mean? (5 points) (c) What is the probability that [pic] will differ
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SPSS: Grouped Frequency Distribution FIRST STEP: Under the Transform menu‚ choose Visual Binning… This command assists you in creating a new variable that groups the data. You will then use the new variable to create a grouped frequency distribution. • From the Variables list box‚ click on wt (weight) and then on the arrow to move it to the Variable to Band list box. Click Continue. • Select wt in the left box. Near the top of this dialog box‚ enter a name for your new variable (such
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