The average number of miles (in thousands) that a car's tire will function before needing replacement is 74 and the standard deviation is 19. Suppose that 45 randomly selected tires are tested. Round all answers to 4 decimal places where possible and assume a normal distribution. What is the distribution of XX? XX ~ N(,) What is the distribution of ¯xx¯? ¯xx¯ ~ N(,) If a randomly selected individual tire is tested, find the probability that the number of miles (in thousands) before it will need replacement is between 74.3 and 78.1.

MATLAB: An Introduction with Applications
6th Edition
ISBN:9781119256830
Author:Amos Gilat
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Chapter1: Starting With Matlab
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The average number of miles (in thousands) that a car's tire will function before needing replacement is 74 and the standard deviation is 19. Suppose that 45 randomly selected tires are tested. Round all answers to 4 decimal places where possible and assume a normal distribution.

  1. What is the distribution of XX? XX ~ N(,)
  2. What is the distribution of ¯xx¯? ¯xx¯ ~ N(,)
  3. If a randomly selected individual tire is tested, find the probability that the number of miles (in thousands) before it will need replacement is between 74.3 and 78.1. 
  4. For the 45 tires tested, find the probability that the average miles (in thousands) before need of replacement is between 74.3 and 78.1. 
  5. For part d), is the assumption that the distribution is normal necessary? NoYes
  6.  
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