F17_latestart M13A7_40492 Intro Statistics (T Th 3-5:15P) wesley xiao& 11/13/17

Question

F17_latestart M13A7_40492 Intro Statistics (T Th 3-5:15P) wesley xiao& 11/13/17 10:28 PM Homework: Section 5.4 Homework Save Score: 0.5 of 1 pt 12 of 13 (12 complete) HW Score: 60.77%, 7.9 of 13 pts 5.4.38 Question Help * A manufacturer claims that the life span of its tires is 52,000 miles. You work for a consumer protection agency and you are testing these tires. Assume the life spans of the tires are normally distributed. You select 100 tires at random and test them. The mean life span is 51,836 miles. Assume = 800, Complete parts (a) through (c). (a) Assuming the manufacturers claim is correct, what is the probability that the mean of the sample is 51,836 miles or less? (Round to four decimal places as needed.) Enter your answer in the answer box and then click Check Answer 0,6KJ s 59% parts remaining Clear All Check Ans0.4Ks

Explanation / Answer

here std error of mean =std deviation/(n)1/2 =800/(100)1/2 =80

therefore probability that the mean of the sample is 51836 miles or less =P(X<51836)=P(Z<(51836-52000)/80)

=P(Z<-2.05)=0.0202

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