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February 25th, 2010, 11:01 PM  #1 
Newbie Joined: Feb 2010 Posts: 1 Thanks: 0  Statistics Normal Distribution Question
Hi Everyone! I need help with a statistics problem: Lori just bought a set of four tires for her car. The life of each tire is normally distributed with a mean of 45,000 miles and a standard deviation of 2000 miles. Find the probability that all four tires will last at least 46,000 miles. Assume that the life of each tire is independent of the lives of other tires. So I tried solving this, but I got stuck with the idea of the probability for all four tires. Am I supposed to multiply the z number of one tire by four?? Thanks. 
February 26th, 2010, 07:23 PM  #2 
Senior Member Joined: Aug 2008 From: Blacksburg VA USA Posts: 344 Thanks: 6 Math Focus: primes of course  Re: Statistics Normal Distribution Question
well, I would ask you a few questions  do you know how the "independent" caveat plays into things, and if so, what approx answer would you xpect if the question posed were for 45000 ie the meanline? Would you say odds are High or low? Or, is it easier to think of 4 playing cards randomly selected from 52 each time, what are odds all 4 cards are value 8 or higher (Ace high)?


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